diff --git a/Library/Homebrew/.rubocop.yml b/Library/Homebrew/.rubocop.yml
index 58b911ca9f..267641f022 100644
--- a/Library/Homebrew/.rubocop.yml
+++ b/Library/Homebrew/.rubocop.yml
@@ -88,3 +88,7 @@ Style/HashSyntax:
 # so many of these in formulae but none in here
 Style/TrailingBodyOnMethodDefinition:
   Enabled: true
+
+Rspec/ExpectActual:
+  Exclude:
+    - 'test/missing_formula_spec.rb'
diff --git a/Library/Homebrew/PATH.rb b/Library/Homebrew/PATH.rb
index de7167eb4b..263f26484e 100644
--- a/Library/Homebrew/PATH.rb
+++ b/Library/Homebrew/PATH.rb
@@ -32,7 +32,7 @@ class PATH
   end
 
   def to_ary
-    @paths
+    @paths.dup.to_ary
   end
   alias to_a to_ary
 
diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index f31224ab25..d571f7e5c6 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -14,12 +14,13 @@ end
 
 require "pathname"
 HOMEBREW_LIBRARY_PATH = Pathname.new(__FILE__).realpath.parent
+
 require "English"
 unless $LOAD_PATH.include?(HOMEBREW_LIBRARY_PATH.to_s)
   $LOAD_PATH.unshift(HOMEBREW_LIBRARY_PATH.to_s)
 end
+
 require "global"
-require "tap"
 
 if ARGV == %w[--version] || ARGV == %w[-v]
   puts "Homebrew #{HOMEBREW_VERSION}"
diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index 3c494428f0..da7d63cdf7 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -1,4 +1,3 @@
-require "set"
 
 class BuildEnvironment
   def initialize(*settings)
diff --git a/Library/Homebrew/cask/lib/hbc.rb b/Library/Homebrew/cask/lib/hbc.rb
index d865b31f2f..a013f4a323 100644
--- a/Library/Homebrew/cask/lib/hbc.rb
+++ b/Library/Homebrew/cask/lib/hbc.rb
@@ -1,5 +1,4 @@
 require "hardware"
-require "utils"
 
 require "hbc/artifact"
 require "hbc/audit"
@@ -20,8 +19,6 @@ require "hbc/locations"
 require "hbc/config"
 require "hbc/macos"
 require "hbc/pkg"
-require "hbc/qualified_token"
-require "hbc/scopes"
 require "hbc/staged"
 require "hbc/system_command"
 require "hbc/topological_hash"
@@ -32,7 +29,6 @@ require "hbc/version"
 
 module Hbc
   include Locations
-  include Scopes
   include Utils
 
   def self.init
diff --git a/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb b/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
index d299733d89..9776a42ae7 100644
--- a/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
+++ b/Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb
@@ -1,4 +1,3 @@
-require "pathname"
 require "timeout"
 
 require "hbc/artifact/abstract_artifact"
diff --git a/Library/Homebrew/cask/lib/hbc/cask.rb b/Library/Homebrew/cask/lib/hbc/cask.rb
index 681130c1b1..410dcfe649 100644
--- a/Library/Homebrew/cask/lib/hbc/cask.rb
+++ b/Library/Homebrew/cask/lib/hbc/cask.rb
@@ -3,11 +3,20 @@ require "hbc/metadata"
 
 module Hbc
   class Cask
+    extend Enumerable
     extend Forwardable
     include Metadata
 
     attr_reader :token, :sourcefile_path, :config
 
+    def self.each
+      return to_enum unless block_given?
+
+      Tap.flat_map(&:cask_files).each do |f|
+        yield CaskLoader::FromTapPathLoader.new(f).load
+      end
+    end
+
     def tap
       return super if block_given? # Object#tap
       @tap
@@ -43,11 +52,13 @@ module Hbc
     end
 
     def full_name
-      if @tap.nil? || @tap == Hbc.default_tap
-        token
-      else
-        "#{@tap}/#{token}"
-      end
+      return token if tap == Hbc.default_tap
+      qualified_token
+    end
+
+    def qualified_token
+      return token if tap.nil?
+      "#{tap.name}/#{token}"
     end
 
     def installed?
diff --git a/Library/Homebrew/cask/lib/hbc/caskroom.rb b/Library/Homebrew/cask/lib/hbc/caskroom.rb
index b5c947f4b1..6c69e5fb8e 100644
--- a/Library/Homebrew/cask/lib/hbc/caskroom.rb
+++ b/Library/Homebrew/cask/lib/hbc/caskroom.rb
@@ -15,5 +15,17 @@ module Hbc
       SystemCommand.run("/usr/sbin/chown", args: [Utils.current_user, Hbc.caskroom], sudo: sudo)
       SystemCommand.run("/usr/bin/chgrp", args: ["admin", Hbc.caskroom], sudo: sudo)
     end
+
+    def casks
+      Pathname.glob(Hbc.caskroom.join("*")).sort.select(&:directory?).map do |path|
+        token = path.basename.to_s
+
+        if tap_path = CaskLoader.tap_paths(token).first
+          next CaskLoader::FromTapPathLoader.new(tap_path).load
+        end
+
+        CaskLoader::FromPathLoader.new(Pathname.glob(path.join(".metadata/*/*/*/*.rb")).first).load
+      end
+    end
   end
 end
diff --git a/Library/Homebrew/cask/lib/hbc/cli/audit.rb b/Library/Homebrew/cask/lib/hbc/cli/audit.rb
index 35d82800c6..2b89a8d2c3 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/audit.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/audit.rb
@@ -9,7 +9,7 @@ module Hbc
       end
 
       def run
-        failed_casks = casks(alternative: -> { Hbc.all })
+        failed_casks = casks(alternative: -> { Cask.to_a })
                        .reject { |cask| audit(cask) }
 
         return if failed_casks.empty?
diff --git a/Library/Homebrew/cask/lib/hbc/cli/info.rb b/Library/Homebrew/cask/lib/hbc/cli/info.rb
index f12fe55648..991f0534ae 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/info.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/info.rb
@@ -60,16 +60,12 @@ module Hbc
       end
 
       def self.repo_info(cask)
-        user, repo, token = QualifiedToken.parse(Hbc.all_tokens.detect { |t| t.split("/").last == cask.token })
+        return if cask.tap.nil?
 
-        return if user.nil? || repo.nil?
-
-        remote_tap = Tap.fetch(user, repo)
-
-        url = if remote_tap.custom_remote? && !remote_tap.remote.nil?
-          remote_tap.remote
+        url = if cask.tap.custom_remote? && !cask.tap.remote.nil?
+          cask.tap.remote
         else
-          "#{remote_tap.default_remote}/blob/master/Casks/#{token}.rb"
+          "#{cask.tap.default_remote}/blob/master/Casks/#{cask.token}.rb"
         end
 
         puts "From: #{Formatter.url(url)}"
diff --git a/Library/Homebrew/cask/lib/hbc/cli/internal_stanza.rb b/Library/Homebrew/cask/lib/hbc/cli/internal_stanza.rb
index bdb1c0c30a..355f1a4d3f 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/internal_stanza.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/internal_stanza.rb
@@ -58,7 +58,7 @@ module Hbc
           @stanza = :artifacts
         end
 
-        casks(alternative: -> { Hbc.all }).each do |cask|
+        casks(alternative: -> { Cask.to_a }).each do |cask|
           print "#{cask}\t" if table?
 
           begin
diff --git a/Library/Homebrew/cask/lib/hbc/cli/list.rb b/Library/Homebrew/cask/lib/hbc/cli/list.rb
index 4a50ae74ad..788b0eede5 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/list.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/list.rb
@@ -37,7 +37,7 @@ module Hbc
       end
 
       def list_installed
-        installed_casks = Hbc.installed
+        installed_casks = Caskroom.casks
 
         if one?
           puts installed_casks.map(&:to_s)
diff --git a/Library/Homebrew/cask/lib/hbc/cli/outdated.rb b/Library/Homebrew/cask/lib/hbc/cli/outdated.rb
index b0a84e8d26..593fea19da 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/outdated.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/outdated.rb
@@ -10,7 +10,7 @@ module Hbc
       end
 
       def run
-        casks(alternative: -> { Hbc.installed }).each do |cask|
+        casks(alternative: -> { Caskroom.casks }).each do |cask|
           odebug "Checking update info of Cask #{cask}"
           self.class.list_if_outdated(cask, greedy?, verbose?)
         end
diff --git a/Library/Homebrew/cask/lib/hbc/cli/search.rb b/Library/Homebrew/cask/lib/hbc/cli/search.rb
index d56d0c81fe..480d7b5e54 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/search.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/search.rb
@@ -3,7 +3,7 @@ module Hbc
     class Search < AbstractCommand
       def run
         if args.empty?
-          puts Formatter.columns(CLI.nice_listing(Hbc.all_tokens))
+          puts Formatter.columns(CLI.nice_listing(Cask.map(&:qualified_token)))
         else
           results = self.class.search(*args)
           self.class.render_results(*results)
@@ -30,6 +30,7 @@ module Hbc
           opoo "Error searching on GitHub: #{error}\n"
           []
         end
+
         matches.map do |match|
           tap = Tap.fetch(match["repository"]["full_name"])
           next if tap.installed?
@@ -42,7 +43,7 @@ module Hbc
         partial_matches = []
         search_term = arguments.join(" ")
         search_regexp = extract_regexp arguments.first
-        all_tokens = CLI.nice_listing(Hbc.all_tokens)
+        all_tokens = CLI.nice_listing(Cask.map(&:qualified_token))
         if search_regexp
           search_term = arguments.first
           partial_matches = all_tokens.grep(/#{search_regexp}/i)
@@ -65,7 +66,7 @@ module Hbc
           return
         end
 
-        if !exact_match && partial_matches.empty?
+        if !exact_match && partial_matches.empty? && remote_matches.empty?
           puts "No Cask found for \"#{search_term}\"."
           return
         end
diff --git a/Library/Homebrew/cask/lib/hbc/cli/style.rb b/Library/Homebrew/cask/lib/hbc/cli/style.rb
index 261bed50b9..cb2e5e0537 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/style.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/style.rb
@@ -27,7 +27,7 @@ module Hbc
 
       def cask_paths
         @cask_paths ||= if args.empty?
-          Hbc.all_tapped_cask_dirs
+          Tap.map(&:cask_dir).select(&:directory?)
         elsif args.any? { |file| File.exist?(file) }
           args
         else
diff --git a/Library/Homebrew/cask/lib/hbc/cli/upgrade.rb b/Library/Homebrew/cask/lib/hbc/cli/upgrade.rb
index 808b64c4b7..276b180aa1 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/upgrade.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/upgrade.rb
@@ -13,7 +13,7 @@ module Hbc
 
       def run
         outdated_casks = casks(alternative: lambda {
-          Hbc.installed.select do |cask|
+          Caskroom.casks.select do |cask|
             cask.outdated?(greedy?)
           end
         }).select { |cask| cask.outdated?(true) }
diff --git a/Library/Homebrew/cask/lib/hbc/container/bzip2.rb b/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
index 9f2a59bb8a..efa95376a2 100644
--- a/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/bzip2.rb
@@ -1,5 +1,3 @@
-require "tmpdir"
-
 require "hbc/container/base"
 
 module Hbc
diff --git a/Library/Homebrew/cask/lib/hbc/container/cab.rb b/Library/Homebrew/cask/lib/hbc/container/cab.rb
index 327aece6ea..403abcc0fd 100644
--- a/Library/Homebrew/cask/lib/hbc/container/cab.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/cab.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/dmg.rb b/Library/Homebrew/cask/lib/hbc/container/dmg.rb
index c0e43f68a0..fcb9b5739d 100644
--- a/Library/Homebrew/cask/lib/hbc/container/dmg.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/dmg.rb
@@ -1,4 +1,3 @@
-require "set"
 require "tempfile"
 
 require "hbc/container/base"
diff --git a/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb b/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
index 63ab917ea2..6a05edb8d0 100644
--- a/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/generic_unar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/gpg.rb b/Library/Homebrew/cask/lib/hbc/container/gpg.rb
index 09c75468ac..ae162565e8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/gpg.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/gpg.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/gzip.rb b/Library/Homebrew/cask/lib/hbc/container/gzip.rb
index d3dd7b8fd0..4f91c3879c 100644
--- a/Library/Homebrew/cask/lib/hbc/container/gzip.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/gzip.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/lzma.rb b/Library/Homebrew/cask/lib/hbc/container/lzma.rb
index 1e165ba2a7..7d50199bc8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/lzma.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/lzma.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/tar.rb b/Library/Homebrew/cask/lib/hbc/container/tar.rb
index eb646c816f..f5340174e4 100644
--- a/Library/Homebrew/cask/lib/hbc/container/tar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/tar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/xar.rb b/Library/Homebrew/cask/lib/hbc/container/xar.rb
index a0165ca57e..9121e726d8 100644
--- a/Library/Homebrew/cask/lib/hbc/container/xar.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/xar.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/xz.rb b/Library/Homebrew/cask/lib/hbc/container/xz.rb
index 4086ae1886..408e0917a5 100644
--- a/Library/Homebrew/cask/lib/hbc/container/xz.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/xz.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 
 require "hbc/container/base"
 
diff --git a/Library/Homebrew/cask/lib/hbc/dsl.rb b/Library/Homebrew/cask/lib/hbc/dsl.rb
index 9a88f1b624..9d229e2880 100644
--- a/Library/Homebrew/cask/lib/hbc/dsl.rb
+++ b/Library/Homebrew/cask/lib/hbc/dsl.rb
@@ -1,4 +1,3 @@
-require "set"
 require "locale"
 
 require "hbc/artifact"
diff --git a/Library/Homebrew/cask/lib/hbc/locations.rb b/Library/Homebrew/cask/lib/hbc/locations.rb
index 40ba2989f0..fea696e5b0 100644
--- a/Library/Homebrew/cask/lib/hbc/locations.rb
+++ b/Library/Homebrew/cask/lib/hbc/locations.rb
@@ -1,4 +1,3 @@
-require "tap"
 
 module Hbc
   module Locations
diff --git a/Library/Homebrew/cask/lib/hbc/macos.rb b/Library/Homebrew/cask/lib/hbc/macos.rb
index d47e04fb24..c983c1e24e 100644
--- a/Library/Homebrew/cask/lib/hbc/macos.rb
+++ b/Library/Homebrew/cask/lib/hbc/macos.rb
@@ -1,4 +1,3 @@
-require "set"
 
 require "os/mac/version"
 
@@ -239,26 +238,35 @@ module OS
 
     # TODO: There should be a way to specify a containing
     #       directory under which nothing can be deleted.
-    UNDELETABLE_DIRS = [
+    UNDELETABLE_PATHS = [
       "~/",
       "~/Applications",
+      "~/Applications/.localized",
       "~/Desktop",
+      "~/Desktop/.localized",
       "~/Documents",
+      "~/Documents/.localized",
       "~/Downloads",
+      "~/Downloads/.localized",
       "~/Mail",
       "~/Movies",
+      "~/Movies/.localized",
       "~/Music",
+      "~/Music/.localized",
       "~/Music/iTunes",
       "~/Music/iTunes/iTunes Music",
       "~/Music/iTunes/Album Artwork",
       "~/News",
       "~/Pictures",
+      "~/Pictures/.localized",
       "~/Pictures/Desktops",
       "~/Pictures/Photo Booth",
       "~/Pictures/iChat Icons",
       "~/Pictures/iPhoto Library",
       "~/Public",
+      "~/Public/.localized",
       "~/Sites",
+      "~/Sites/.localized",
       "~/Library",
       "~/Library/.localized",
       "~/Library/Accessibility",
@@ -365,17 +373,17 @@ module OS
       "~/Library/Widgets",
       "~/Library/Workflows",
     ]
-                       .map { |x| Pathname(x.sub(%r{^~(?=(/|$))}, Dir.home)).expand_path }
-                       .to_set
-                       .union(SYSTEM_DIRS)
-                       .freeze
+                        .map { |path| Pathname(path.sub(%r{^~(?=(/|$))}, Dir.home)).expand_path }
+                        .to_set
+                        .union(SYSTEM_DIRS)
+                        .freeze
 
     def system_dir?(dir)
       SYSTEM_DIRS.include?(Pathname.new(dir).expand_path)
     end
 
-    def undeletable?(dir)
-      UNDELETABLE_DIRS.include?(Pathname.new(dir).expand_path)
+    def undeletable?(path)
+      UNDELETABLE_PATHS.include?(Pathname.new(path).expand_path)
     end
   end
 end
diff --git a/Library/Homebrew/cask/lib/hbc/metadata.rb b/Library/Homebrew/cask/lib/hbc/metadata.rb
index 344c38ceea..030b18dd9f 100644
--- a/Library/Homebrew/cask/lib/hbc/metadata.rb
+++ b/Library/Homebrew/cask/lib/hbc/metadata.rb
@@ -22,7 +22,7 @@ module Hbc
       end
 
       path = if timestamp == :latest
-        Pathname.glob(metadata_versioned_path(version: version).join("*")).sort.last
+        Pathname.glob(metadata_versioned_path(version: version).join("*")).max
       else
         timestamp = new_timestamp if timestamp == :now
         metadata_versioned_path(version: version).join(timestamp)
diff --git a/Library/Homebrew/cask/lib/hbc/qualified_token.rb b/Library/Homebrew/cask/lib/hbc/qualified_token.rb
deleted file mode 100644
index 09eedef1b3..0000000000
--- a/Library/Homebrew/cask/lib/hbc/qualified_token.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-module Hbc
-  module QualifiedToken
-    def self.parse(arg)
-      return nil unless arg.is_a?(String)
-      return nil unless match = arg.downcase.match(HOMEBREW_TAP_CASK_REGEX)
-      user, repo, token = match.captures
-      odebug "[user, repo, token] might be [#{user}, #{repo}, #{token}]"
-      [user, repo, token]
-    end
-  end
-end
diff --git a/Library/Homebrew/cask/lib/hbc/scopes.rb b/Library/Homebrew/cask/lib/hbc/scopes.rb
deleted file mode 100644
index a469ae0fa6..0000000000
--- a/Library/Homebrew/cask/lib/hbc/scopes.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-module Hbc
-  module Scopes
-    def self.included(base)
-      base.extend(ClassMethods)
-    end
-
-    module ClassMethods
-      def all
-        all_tokens.map(&CaskLoader.public_method(:load))
-      end
-
-      def all_tapped_cask_dirs
-        Tap.map(&:cask_dir).select(&:directory?)
-      end
-
-      def all_tokens
-        Tap.flat_map do |t|
-          t.cask_files.map do |p|
-            "#{t.name}/#{File.basename(p, ".rb")}"
-          end
-        end
-      end
-
-      def installed
-        # CaskLoader.load has some DWIM which is slow.  Optimize here
-        # by spoon-feeding CaskLoader.load fully-qualified paths.
-        # TODO: speed up Hbc::Source::Tapped (main perf drag is calling Hbc.all_tokens repeatedly)
-        # TODO: ability to specify expected source when calling CaskLoader.load (minor perf benefit)
-        Pathname.glob(caskroom.join("*"))
-                .sort
-                .map do |caskroom_path|
-                  token = caskroom_path.basename.to_s
-
-                  path_to_cask = all_tapped_cask_dirs.find do |tap_dir|
-                    tap_dir.join("#{token}.rb").exist?
-                  end
-
-                  if path_to_cask
-                    CaskLoader.load(path_to_cask.join("#{token}.rb"))
-                  else
-                    CaskLoader.load(token)
-                  end
-                end
-      end
-    end
-  end
-end
diff --git a/Library/Homebrew/cask/lib/hbc/staged.rb b/Library/Homebrew/cask/lib/hbc/staged.rb
index da097e0cf9..fa2439a2e5 100644
--- a/Library/Homebrew/cask/lib/hbc/staged.rb
+++ b/Library/Homebrew/cask/lib/hbc/staged.rb
@@ -33,6 +33,7 @@ module Hbc
     def set_ownership(paths, user: current_user, group: "staff")
       full_paths = remove_nonexistent(paths)
       return if full_paths.empty?
+      ohai "Changing ownership of paths required by #{@cask}; your password may be necessary"
       @command.run!("/usr/sbin/chown", args: ["-R", "--", "#{user}:#{group}"] + full_paths,
                                        sudo: true)
     end
diff --git a/Library/Homebrew/cask/lib/hbc/utils.rb b/Library/Homebrew/cask/lib/hbc/utils.rb
index 0f44c0157f..01ab4dad7f 100644
--- a/Library/Homebrew/cask/lib/hbc/utils.rb
+++ b/Library/Homebrew/cask/lib/hbc/utils.rb
@@ -4,17 +4,6 @@ require "stringio"
 
 BUG_REPORTS_URL = "https://github.com/caskroom/homebrew-cask#reporting-bugs".freeze
 
-class Buffer < StringIO
-  extend Predicable
-
-  attr_predicate :tty?
-
-  def initialize(tty = false)
-    super()
-    @tty = tty
-  end
-end
-
 # global methods
 
 def odebug(title, *sput)
diff --git a/Library/Homebrew/caveats.rb b/Library/Homebrew/caveats.rb
index a289a12202..9fb788a46f 100644
--- a/Library/Homebrew/caveats.rb
+++ b/Library/Homebrew/caveats.rb
@@ -1,4 +1,3 @@
-require "forwardable"
 require "language/python"
 
 class Caveats
diff --git a/Library/Homebrew/cli_parser.rb b/Library/Homebrew/cli_parser.rb
index 8a6e15abb7..dd467f3fc6 100644
--- a/Library/Homebrew/cli_parser.rb
+++ b/Library/Homebrew/cli_parser.rb
@@ -11,16 +11,20 @@ module Homebrew
       def initialize(&block)
         @parser = OptionParser.new
         @parsed_args = OpenStruct.new
+        # undefine tap to allow --tap argument
+        @parsed_args.instance_eval { undef tap }
         instance_eval(&block)
       end
 
       def switch(*names, description: nil, env: nil)
         description = option_to_description(*names) if description.nil?
-        names, env = common_switch(*names) if names.first.is_a?(Symbol)
+        global_switch = names.first.is_a?(Symbol)
+        names, env = common_switch(*names) if global_switch
         @parser.on(*names, description) do
-          enable_switch(*names)
+          enable_switch(*names, global_switch)
         end
-        enable_switch(*names) if !env.nil? && !ENV["HOMEBREW_#{env.to_s.upcase}"].nil?
+        enable_switch(*names, global_switch) if !env.nil? &&
+                                                !ENV["HOMEBREW_#{env.to_s.upcase}"].nil?
       end
 
       def comma_array(name, description: nil)
@@ -30,14 +34,15 @@ module Homebrew
         end
       end
 
-      def flag(name, description: nil, required: false)
-        if required
-          option_required = OptionParser::REQUIRED_ARGUMENT
+      def flag(name, description: nil)
+        if name.end_with? "="
+          required = OptionParser::REQUIRED_ARGUMENT
+          name.chomp! "="
         else
-          option_required = OptionParser::OPTIONAL_ARGUMENT
+          required = OptionParser::OPTIONAL_ARGUMENT
         end
         description = option_to_description(name) if description.nil?
-        @parser.on(name, description, option_required) do |option_value|
+        @parser.on(name, description, required) do |option_value|
           @parsed_args[option_to_name(name)] = option_value
         end
       end
@@ -47,27 +52,33 @@ module Homebrew
       end
 
       def option_to_description(*names)
-        names.map { |name| name.to_s.sub(/\A--?/, "").tr("-", " ") }.sort.last
+        names.map { |name| name.to_s.sub(/\A--?/, "").tr("-", " ") }.max
       end
 
       def parse(cmdline_args = ARGV)
-        @parser.parse!(cmdline_args)
+        @parser.parse(cmdline_args)
         @parsed_args
       end
 
       private
 
-      def enable_switch(*names)
+      def enable_switch(*names, global_switch)
         names.each do |name|
+          if global_switch
+            Homebrew.args["#{option_to_name(name)}?"] = true
+            next
+          end
           @parsed_args["#{option_to_name(name)}?"] = true
         end
       end
 
+      # These are common/global switches accessible throughout Homebrew
       def common_switch(name)
         case name
         when :quiet   then [["-q", "--quiet"], :quiet]
         when :verbose then [["-v", "--verbose"], :verbose]
         when :debug   then [["-d", "--debug"], :debug]
+        when :force   then [["-f", "--force"], :force]
         else name
         end
       end
diff --git a/Library/Homebrew/cmd/--repository.rb b/Library/Homebrew/cmd/--repository.rb
index 006d4cd5d3..6f6f8d31ec 100644
--- a/Library/Homebrew/cmd/--repository.rb
+++ b/Library/Homebrew/cmd/--repository.rb
@@ -4,8 +4,6 @@
 #:  * `--repository` <user>`/`<repo>:
 #:    Display where tap <user>`/`<repo>'s directory is located.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/cleanup.rb b/Library/Homebrew/cmd/cleanup.rb
index 290b748de2..2fba06e20f 100644
--- a/Library/Homebrew/cmd/cleanup.rb
+++ b/Library/Homebrew/cmd/cleanup.rb
@@ -12,7 +12,6 @@
 #:    deleted. If you want to delete those too: `rm -rf $(brew --cache)`
 
 require "cleanup"
-require "utils"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/cmd/doctor.rb b/Library/Homebrew/cmd/doctor.rb
index 4e439fa0a3..216987077c 100644
--- a/Library/Homebrew/cmd/doctor.rb
+++ b/Library/Homebrew/cmd/doctor.rb
@@ -28,7 +28,6 @@ module Homebrew
       slow_checks = %w[
         check_for_broken_symlinks
         check_missing_deps
-        check_for_linked_keg_only_brews
       ]
       methods = (checks.all.sort - slow_checks) + slow_checks
     else
diff --git a/Library/Homebrew/cmd/gist-logs.rb b/Library/Homebrew/cmd/gist-logs.rb
index c30ee85cd9..df87b327c8 100644
--- a/Library/Homebrew/cmd/gist-logs.rb
+++ b/Library/Homebrew/cmd/gist-logs.rb
@@ -119,7 +119,7 @@ module Homebrew
   def create_issue(repo, title, body)
     url = "https://api.github.com/repos/#{repo}/issues"
     data = { "title" => title, "body" => body }
-    scopes = GitHub::CREATE_ISSUE_SCOPES
+    scopes = GitHub::CREATE_ISSUE_FORK_OR_PR_SCOPES
     GitHub.open_api(url, data: data, scopes: scopes)["html_url"]
   end
 
diff --git a/Library/Homebrew/cmd/help.rb b/Library/Homebrew/cmd/help.rb
index 2b1e7c5049..fa5727816e 100644
--- a/Library/Homebrew/cmd/help.rb
+++ b/Library/Homebrew/cmd/help.rb
@@ -1,7 +1,7 @@
 HOMEBREW_HELP = <<~EOS.freeze
   Example usage:
     brew search [TEXT|/REGEX/]
-    brew (info|home|options) [FORMULA...]
+    brew info [FORMULA...]
     brew install FORMULA...
     brew update
     brew upgrade [FORMULA...]
@@ -11,17 +11,17 @@ HOMEBREW_HELP = <<~EOS.freeze
   Troubleshooting:
     brew config
     brew doctor
-    brew install -vd FORMULA
+    brew install --verbose --debug FORMULA
 
-  Developers:
+  Contributing:
     brew create [URL [--no-fetch]]
     brew edit [FORMULA...]
-    https://docs.brew.sh/Formula-Cookbook
 
   Further help:
-    man brew
+    brew commands
     brew help [COMMAND]
-    brew home
+    man brew
+    https://docs.brew.sh
 EOS
 
 # NOTE Keep the lenth of vanilla --help less than 25 lines!
diff --git a/Library/Homebrew/cmd/info.rb b/Library/Homebrew/cmd/info.rb
index a0e1cd4756..cfe8b13d87 100644
--- a/Library/Homebrew/cmd/info.rb
+++ b/Library/Homebrew/cmd/info.rb
@@ -60,7 +60,7 @@ module Homebrew
         rescue FormulaUnavailableError => e
           ofail e.message
           # No formula with this name, try a missing formula lookup
-          if (reason = Homebrew::MissingFormula.reason(f))
+          if (reason = MissingFormula.reason(f))
             $stderr.puts reason
           end
         end
diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index e26499a21f..21ea88193a 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -71,7 +71,6 @@ require "missing_formula"
 require "diagnostic"
 require "cmd/search"
 require "formula_installer"
-require "tap"
 require "hardware"
 require "development_tools"
 
@@ -166,7 +165,8 @@ module Homebrew
             formulae << f
           else
             opoo <<~EOS
-              #{f.full_name} #{f.pkg_version} is already installed
+              #{f.full_name} #{f.pkg_version} is already installed and up-to-date
+              To reinstall #{f.pkg_version}, run `brew reinstall #{f.name}`
             EOS
           end
         elsif (ARGV.build_head? && new_head_installed) || prefix_installed
@@ -190,12 +190,17 @@ module Homebrew
             EOS
           elsif !f.linked? || f.keg_only?
             msg = <<~EOS
-              #{msg}, it's just not linked.
+              #{msg}, it's just not linked
               You can use `brew link #{f}` to link this version.
             EOS
           elsif ARGV.only_deps?
             msg = nil
             formulae << f
+          else
+            msg = <<~EOS
+              #{msg} and up-to-date
+              To reinstall #{f.pkg_version}, run `brew reinstall #{f.name}`
+            EOS
           end
           opoo msg if msg
         elsif !f.any_version_installed? && old_formula = f.old_installed_formulae.first
@@ -252,7 +257,7 @@ module Homebrew
       end
 
       ofail e.message
-      if (reason = Homebrew::MissingFormula.reason(e.name))
+      if (reason = MissingFormula.reason(e.name))
         $stderr.puts reason
         return
       end
diff --git a/Library/Homebrew/cmd/leaves.rb b/Library/Homebrew/cmd/leaves.rb
index 42fa18a28a..ec5238c2a1 100644
--- a/Library/Homebrew/cmd/leaves.rb
+++ b/Library/Homebrew/cmd/leaves.rb
@@ -3,7 +3,6 @@
 
 require "formula"
 require "tab"
-require "set"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/cmd/linkapps.rb b/Library/Homebrew/cmd/linkapps.rb
deleted file mode 100644
index 1bec67a047..0000000000
--- a/Library/Homebrew/cmd/linkapps.rb
+++ /dev/null
@@ -1,67 +0,0 @@
-#: @hide_from_man_page
-#:  * `linkapps` [`--local`] [<formulae>]:
-#:    Find installed formulae that provide `.app`-style macOS apps and symlink them
-#:    into `/Applications`, allowing for easier access (deprecated).
-#:
-#:    Unfortunately `brew linkapps` cannot behave nicely with e.g. Spotlight using
-#:    either aliases or symlinks and Homebrew formulae do not build "proper" `.app`
-#:    bundles that can be relocated. Instead, please consider using `brew cask` and
-#:    migrate formulae using `.app`s to casks.
-
-require "keg"
-require "formula"
-
-module Homebrew
-  module_function
-
-  def linkapps
-    odeprecated "'brew linkapps'"
-
-    target_dir = linkapps_target(local: ARGV.include?("--local"))
-
-    unless target_dir.directory?
-      opoo "#{target_dir} does not exist, stopping."
-      puts "Run `mkdir #{target_dir}` first."
-      exit 1
-    end
-
-    if ARGV.named.empty?
-      kegs = Formula.racks.map do |rack|
-        keg = rack.subdirs.map { |d| Keg.new(d) }
-        next if keg.empty?
-        keg.detect(&:linked?) || keg.max_by(&:version)
-      end
-    else
-      kegs = ARGV.kegs
-    end
-
-    link_count = 0
-    kegs.each do |keg|
-      keg.apps.each do |app|
-        puts "Linking: #{app}"
-        target_app = target_dir/app.basename
-
-        if target_app.exist? && !target_app.symlink?
-          onoe "#{target_app} already exists, skipping."
-          next
-        end
-
-        # We prefer system `ln` over `FileUtils.ln_sf` because the latter seems
-        # to have weird failure conditions (that were observed in the past).
-        system "ln", "-sf", app, target_dir
-        link_count += 1
-      end
-    end
-
-    if link_count.zero?
-      puts "No apps linked to #{target_dir}" if ARGV.verbose?
-    else
-      puts "Linked #{Formatter.pluralize(link_count, "app")} to #{target_dir}"
-    end
-  end
-
-  def linkapps_target(opts = {})
-    local = opts.fetch(:local, false)
-    Pathname.new(local ? "~/Applications" : "/Applications").expand_path
-  end
-end
diff --git a/Library/Homebrew/cmd/missing.rb b/Library/Homebrew/cmd/missing.rb
index 707ad68345..a12fd5460e 100644
--- a/Library/Homebrew/cmd/missing.rb
+++ b/Library/Homebrew/cmd/missing.rb
@@ -4,6 +4,8 @@
 #:
 #:    If `--hide=`<hidden> is passed, act as if none of <hidden> are installed.
 #:    <hidden> should be a comma-separated list of formulae.
+#:
+#:    `missing` exits with a non-zero status if any formulae are missing dependencies.
 
 require "formula"
 require "tab"
@@ -25,6 +27,7 @@ module Homebrew
       missing = f.missing_dependencies(hide: ARGV.values("hide"))
       next if missing.empty?
 
+      Homebrew.failed = true
       print "#{f}: " if ff.size > 1
       puts missing.join(" ")
     end
diff --git a/Library/Homebrew/cmd/prune.rb b/Library/Homebrew/cmd/prune.rb
index 7ec2838bae..3270066131 100644
--- a/Library/Homebrew/cmd/prune.rb
+++ b/Library/Homebrew/cmd/prune.rb
@@ -1,15 +1,12 @@
 #:  * `prune` [`--dry-run`]:
 #:    Remove dead symlinks from the Homebrew prefix. This is generally not
-#:    needed, but can be useful when doing DIY installations. Also remove broken
-#:    app symlinks from `/Applications` and `~/Applications` that were previously
-#:    created by `brew linkapps`.
+#:    needed, but can be useful when doing DIY installations.
 #:
 #:    If `--dry-run` or `-n` is passed, show what would be removed, but do not
 #:    actually remove anything.
 
 require "keg"
 require "cmd/tap"
-require "cmd/unlinkapps"
 
 module Homebrew
   module_function
@@ -49,17 +46,15 @@ module Homebrew
       end
     end
 
-    unless ARGV.dry_run?
-      if ObserverPathnameExtension.total.zero?
-        puts "Nothing pruned" if ARGV.verbose?
-      else
-        n, d = ObserverPathnameExtension.counts
-        print "Pruned #{n} symbolic links "
-        print "and #{d} directories " if d.positive?
-        puts "from #{HOMEBREW_PREFIX}"
-      end
-    end
+    return if ARGV.dry_run?
 
-    unlinkapps_prune(dry_run: ARGV.dry_run?, quiet: true)
+    if ObserverPathnameExtension.total.zero?
+      puts "Nothing pruned" if ARGV.verbose?
+    else
+      n, d = ObserverPathnameExtension.counts
+      print "Pruned #{n} symbolic links "
+      print "and #{d} directories " if d.positive?
+      puts "from #{HOMEBREW_PREFIX}"
+    end
   end
 end
diff --git a/Library/Homebrew/cmd/search.rb b/Library/Homebrew/cmd/search.rb
index 4ba5247f12..0f01afa46f 100644
--- a/Library/Homebrew/cmd/search.rb
+++ b/Library/Homebrew/cmd/search.rb
@@ -15,8 +15,6 @@
 
 require "formula"
 require "missing_formula"
-require "utils"
-require "official_taps"
 require "descriptions"
 
 module Homebrew
@@ -66,7 +64,7 @@ module Homebrew
         count = local_results.length + tap_results.length
 
         ohai "Searching blacklisted, migrated and deleted formulae..."
-        if reason = Homebrew::MissingFormula.reason(query, silent: true)
+        if reason = MissingFormula.reason(query, silent: true)
           if count.positive?
             puts
             puts "If you meant #{query.inspect} specifically:"
@@ -110,15 +108,22 @@ module Homebrew
       $stderr.puts Formatter.headline("Searching taps on GitHub...", color: :blue)
     end
 
-    valid_dirnames = ["Formula", "HomebrewFormula", "Casks", "."].freeze
-    matches = GitHub.search_code(user: ["Homebrew", "caskroom"], filename: query, extension: "rb")
-
+    matches = begin
+      GitHub.search_code(
+        user: ["Homebrew", "caskroom"],
+        path: ["Formula", "HomebrewFormula", "Casks", "."],
+        filename: query,
+        extension: "rb",
+      )
+    rescue GitHub::Error => error
+      opoo "Error searching on GitHub: #{error}\n"
+      []
+    end
     matches.map do |match|
-      dirname, filename = File.split(match["path"])
-      next unless valid_dirnames.include?(dirname)
+      filename = File.basename(match["path"], ".rb")
       tap = Tap.fetch(match["repository"]["full_name"])
       next if tap.installed? && match["repository"]["owner"]["login"] != "caskroom"
-      "#{tap.name}/#{File.basename(filename, ".rb")}"
+      "#{tap.name}/#{filename}"
     end.compact
   end
 
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index 76d961a7fe..e41f10f97a 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -19,7 +19,6 @@
 #:
 #:    Exits with a non-zero status if any style violations are found.
 
-require "utils"
 require "json"
 require "open3"
 
diff --git a/Library/Homebrew/cmd/switch.rb b/Library/Homebrew/cmd/switch.rb
index 8a378aed79..b0ac32626e 100644
--- a/Library/Homebrew/cmd/switch.rb
+++ b/Library/Homebrew/cmd/switch.rb
@@ -1,5 +1,5 @@
-#:  * `switch` <name> <version>:
-#:    Symlink all of the specific <version> of <name>'s install to Homebrew prefix.
+#:  * `switch` <formula> <version>:
+#:    Symlink all of the specific <version> of <formula>'s install to Homebrew prefix.
 
 require "formula"
 require "keg"
@@ -9,14 +9,15 @@ module Homebrew
   module_function
 
   def switch
-    if ARGV.named.length != 2
-      onoe "Usage: brew switch <name> <version>"
+    name = ARGV.first
+
+    usage = "Usage: brew switch <formula> <version>"
+
+    unless name
+      onoe usage
       exit 1
     end
 
-    name = ARGV.shift
-    version = ARGV.shift
-
     rack = Formulary.to_rack(name)
 
     unless rack.directory?
@@ -24,13 +25,21 @@ module Homebrew
       exit 2
     end
 
-    # Does the target version exist?
+    versions = rack.subdirs
+                   .map { |d| Keg.new(d).version }
+                   .sort
+                   .join(", ")
+    version = ARGV[1]
+
+    if !version || ARGV.named.length > 2
+      onoe usage
+      puts "#{name} installed versions: #{versions}"
+      exit 1
+    end
+
     unless (rack/version).directory?
       onoe "#{name} does not have a version \"#{version}\" in the Cellar."
-
-      versions = rack.subdirs.map { |d| Keg.new(d).version }.sort
-      puts "Versions available: #{versions.join(", ")}"
-
+      puts "#{name} installed versions: #{versions}"
       exit 3
     end
 
diff --git a/Library/Homebrew/cmd/tap-info.rb b/Library/Homebrew/cmd/tap-info.rb
index 26daa1a8ae..b2d9ee5088 100644
--- a/Library/Homebrew/cmd/tap-info.rb
+++ b/Library/Homebrew/cmd/tap-info.rb
@@ -15,8 +15,6 @@
 #:    See the docs for examples of using the JSON output:
 #:    <https://docs.brew.sh/Querying-Brew>
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap-pin.rb b/Library/Homebrew/cmd/tap-pin.rb
index 41957f2652..505720f30d 100644
--- a/Library/Homebrew/cmd/tap-pin.rb
+++ b/Library/Homebrew/cmd/tap-pin.rb
@@ -2,8 +2,6 @@
 #:    Pin <tap>, prioritizing its formulae over core when formula names are supplied
 #:    by the user. See also `tap-unpin`.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap-unpin.rb b/Library/Homebrew/cmd/tap-unpin.rb
index 05bfc7c8b9..0c7c9ee020 100644
--- a/Library/Homebrew/cmd/tap-unpin.rb
+++ b/Library/Homebrew/cmd/tap-unpin.rb
@@ -1,8 +1,6 @@
 #:  * `tap-unpin` <tap>:
 #:    Unpin <tap> so its formulae are no longer prioritized. See also `tap-pin`.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index fa520e2c56..94362f7fe4 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -1,7 +1,7 @@
 #:  * `tap`:
 #:    List all installed taps.
 #:
-#:  * `tap` [`--full`] <user>`/`<repo> [<URL>]:
+#:  * `tap` [`--full`] [`--force-auto-update`] <user>`/`<repo> [<URL>]:
 #:    Tap a formula repository.
 #:
 #:    With <URL> unspecified, taps a formula repository from GitHub using HTTPS.
@@ -18,6 +18,10 @@
 #:    if `--full` is passed, a full clone will be used. To convert a shallow copy
 #:    to a full copy, you can retap passing `--full` without first untapping.
 #:
+#:    By default, only taps hosted on GitHub are auto-updated (for performance
+#:    reasons). If `--force-auto-update` is passed, this tap will be auto-updated
+#:    even if it is not hosted on GitHub.
+#:
 #:    `tap` is re-runnable and exits successfully if there's nothing to do.
 #:    However, retapping with a different <URL> will cause an exception, so first
 #:    `untap` if you need to modify the <URL>.
@@ -25,14 +29,9 @@
 #:  * `tap` `--repair`:
 #:    Migrate tapped formulae from symlink-based to directory-based structure.
 #:
-#:  * `tap` `--list-official`:
-#:    List all official taps.
-#:
 #:  * `tap` `--list-pinned`:
 #:    List all pinned taps.
 
-require "tap"
-
 module Homebrew
   module_function
 
@@ -40,8 +39,7 @@ module Homebrew
     if ARGV.include? "--repair"
       Tap.each(&:link_completions_and_manpages)
     elsif ARGV.include? "--list-official"
-      require "official_taps"
-      puts OFFICIAL_TAPS.map { |t| "homebrew/#{t}" }
+      odeprecated("brew tap --list-official")
     elsif ARGV.include? "--list-pinned"
       puts Tap.select(&:pinned?).map(&:name)
     elsif ARGV.named.empty?
@@ -50,6 +48,7 @@ module Homebrew
       tap = Tap.fetch(ARGV.named[0])
       begin
         tap.install clone_target: ARGV.named[1],
+                    force_auto_update: force_auto_update?,
                     full_clone: full_clone?,
                     quiet: ARGV.quieter?
       rescue TapRemoteMismatchError => e
@@ -62,4 +61,9 @@ module Homebrew
   def full_clone?
     ARGV.include?("--full") || ARGV.homebrew_developer?
   end
+
+  def force_auto_update?
+    # if no relevant flag is present, return nil, meaning "no change"
+    true if ARGV.include?("--force-auto-update")
+  end
 end
diff --git a/Library/Homebrew/cmd/unlinkapps.rb b/Library/Homebrew/cmd/unlinkapps.rb
deleted file mode 100644
index 721e4d6390..0000000000
--- a/Library/Homebrew/cmd/unlinkapps.rb
+++ /dev/null
@@ -1,79 +0,0 @@
-#: @hide_from_man_page
-#:  * `unlinkapps` [`--local`] [`--dry-run`] [<formulae>]:
-#:    Remove symlinks created by `brew linkapps` from `/Applications` (deprecated).
-#:
-#:    Unfortunately `brew linkapps` cannot behave nicely with e.g. Spotlight using
-#:    either aliases or symlinks and Homebrew formulae do not build "proper" `.app`
-#:    bundles that can be relocated. Instead, please consider using `brew cask` and
-#:    migrate formulae using `.app`s to casks.
-
-require "cmd/linkapps"
-
-module Homebrew
-  module_function
-
-  def unlinkapps
-    odeprecated "'brew unlinkapps'"
-
-    target_dir = linkapps_target(local: ARGV.include?("--local"))
-
-    unlinkapps_from_dir(target_dir, dry_run: ARGV.dry_run?)
-  end
-
-  def unlinkapps_prune(opts = {})
-    opts = opts.merge(prune: true)
-    unlinkapps_from_dir(linkapps_target(local: false), opts)
-    unlinkapps_from_dir(linkapps_target(local: true), opts)
-  end
-
-  def unlinkapps_from_dir(target_dir, opts = {})
-    return unless target_dir.directory?
-    dry_run = opts.fetch(:dry_run, false)
-    quiet = opts.fetch(:quiet, false)
-
-    apps = Pathname.glob("#{target_dir}/*.app").select do |app|
-      unlinkapps_unlink?(app, opts)
-    end
-
-    ObserverPathnameExtension.reset_counts!
-
-    app_kind = opts.fetch(:prune, false) ? " (broken link)" : ""
-    apps.each do |app|
-      app.extend(ObserverPathnameExtension)
-      if dry_run
-        puts "Would unlink#{app_kind}: #{app}"
-      else
-        puts "Unlinking#{app_kind}: #{app}" unless quiet
-        app.unlink
-      end
-    end
-
-    return if dry_run
-
-    if ObserverPathnameExtension.total.zero?
-      puts "No apps unlinked from #{target_dir}" if ARGV.verbose?
-    else
-      n = ObserverPathnameExtension.total
-      puts "Unlinked #{Formatter.pluralize(n, "app")} from #{target_dir}"
-    end
-  end
-
-  UNLINKAPPS_PREFIXES = %W[
-    #{HOMEBREW_CELLAR}/
-    #{HOMEBREW_PREFIX}/opt/
-  ].freeze
-
-  def unlinkapps_unlink?(target_app, opts = {})
-    # Skip non-symlinks and symlinks that don't point into the Homebrew prefix.
-    app = target_app.readlink.to_s if target_app.symlink?
-    return false unless app&.start_with?(*UNLINKAPPS_PREFIXES)
-
-    if opts.fetch(:prune, false)
-      !File.exist?(app) # Remove only broken symlinks in prune mode.
-    elsif ARGV.named.empty?
-      true
-    else
-      ARGV.kegs.any? { |keg| app.start_with?("#{keg}/", "#{keg.opt_record}/") }
-    end
-  end
-end
diff --git a/Library/Homebrew/cmd/untap.rb b/Library/Homebrew/cmd/untap.rb
index 0d363b7b58..1b4bf109dd 100644
--- a/Library/Homebrew/cmd/untap.rb
+++ b/Library/Homebrew/cmd/untap.rb
@@ -1,8 +1,6 @@
 #:  * `untap` <tap>:
 #:    Remove a tapped repository.
 
-require "tap"
-
 module Homebrew
   module_function
 
diff --git a/Library/Homebrew/cmd/update-report.rb b/Library/Homebrew/cmd/update-report.rb
index d241d17b06..b2d5dfdbed 100644
--- a/Library/Homebrew/cmd/update-report.rb
+++ b/Library/Homebrew/cmd/update-report.rb
@@ -7,7 +7,6 @@ require "migrator"
 require "formulary"
 require "descriptions"
 require "cleanup"
-require "utils"
 
 module Homebrew
   module_function
diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index f0fbdffafa..d3dae2be31 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -493,8 +493,12 @@ EOS
         [[ -z "$HOMEBREW_UPDATE_FORCE" ]] && [[ "$UPSTREAM_SHA_HTTP_CODE" = "304" ]] && exit
       elif [[ -n "$HOMEBREW_UPDATE_PREINSTALL" ]]
       then
-        # Don't try to do a `git fetch` that may take longer than expected.
-        exit
+        FORCE_AUTO_UPDATE="$(git config homebrew.forceautoupdate 2>/dev/null || echo "false")"
+        if [[ "$FORCE_AUTO_UPDATE" != "true" ]]
+        then
+          # Don't try to do a `git fetch` that may take longer than expected.
+          exit
+        fi
       fi
 
       if [[ -n "$HOMEBREW_VERBOSE" ]]
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index 02bd489a43..340037a2ba 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -29,7 +29,7 @@ module Homebrew
 
     Homebrew.perform_preinstall_checks
 
-    odeprecated "'brew upgrade --all'", "'brew upgrade'" if ARGV.include?("--all")
+    odisabled "'brew upgrade --all'", "'brew upgrade'" if ARGV.include?("--all")
 
     if ARGV.named.empty?
       outdated = Formula.installed.select do |f|
@@ -67,7 +67,14 @@ module Homebrew
       oh1 "No packages to upgrade"
     else
       oh1 "Upgrading #{Formatter.pluralize(formulae_to_install.length, "outdated package")}, with result:"
-      puts formulae_to_install.map { |f| "#{f.full_specified_name} #{f.pkg_version}" } * ", "
+      formulae_upgrades = formulae_to_install.map do |f|
+        if f.optlinked?
+          "#{f.full_specified_name} #{Keg.new(f.opt_prefix).version} -> #{f.pkg_version}"
+        else
+          "#{f.full_specified_name} #{f.pkg_version}"
+        end
+      end
+      puts formulae_upgrades.join(", ")
     end
 
     # Sort keg_only before non-keg_only formulae to avoid any needless conflicts
diff --git a/Library/Homebrew/cmd/uses.rb b/Library/Homebrew/cmd/uses.rb
index 98ecca0f5d..bfc81f040a 100644
--- a/Library/Homebrew/cmd/uses.rb
+++ b/Library/Homebrew/cmd/uses.rb
@@ -54,48 +54,19 @@ module Homebrew
       used_formulae.all? do |ff|
         begin
           deps = f.runtime_dependencies if only_installed_arg
-          if recursive
-            deps ||= recursive_includes(Dependency, f, includes, ignores)
-
-            dep_formulae = deps.flat_map do |dep|
-              begin
-                dep.to_formula
-              rescue
-                []
-              end
-            end
-
-            reqs_by_formula = ([f] + dep_formulae).flat_map do |formula|
-              formula.requirements.map { |req| [formula, req] }
-            end
-
-            reqs_by_formula.reject! do |dependent, req|
-              if req.recommended?
-                ignores.include?("recommended?") || dependent.build.without?(req)
-              elsif req.test?
-                !includes.include?("test?")
-              elsif req.optional?
-                !includes.include?("optional?") && !dependent.build.with?(req)
-              elsif req.build?
-                !includes.include?("build?")
-              end
-            end
-
-            reqs = reqs_by_formula.map(&:last)
+          deps ||= if recursive
+            recursive_includes(Dependency, f, includes, ignores)
           else
-            deps ||= reject_ignores(f.deps, ignores, includes)
-            reqs   = reject_ignores(f.requirements, ignores, includes)
+            reject_ignores(f.deps, ignores, includes)
           end
 
-          next true if deps.any? do |dep|
+          deps.any? do |dep|
             begin
               dep.to_formula.full_name == ff.full_name
             rescue
               dep.name == ff.name
             end
           end
-
-          reqs.any? { |req| req.name == ff.name }
         rescue FormulaUnavailableError
           # Silently ignore this case as we don't care about things used in
           # taps that aren't currently tapped.
diff --git a/Library/Homebrew/cmd/vendor-install.sh b/Library/Homebrew/cmd/vendor-install.sh
index 8aba2174e5..909ff936a3 100644
--- a/Library/Homebrew/cmd/vendor-install.sh
+++ b/Library/Homebrew/cmd/vendor-install.sh
@@ -47,7 +47,15 @@ fetch() {
   local sha
   local temporary_path
 
-  curl_args=(
+  curl_args=()
+
+  # do not load .curlrc unless requested (must be the first argument)
+  if [[ -z "$HOMEBREW_CURLRC" ]]
+  then
+    curl_args[${#curl_args[*]}]="-q"
+  fi
+
+  curl_args+=(
     --fail
     --remote-time
     --location
diff --git a/Library/Homebrew/compat.rb b/Library/Homebrew/compat.rb
index a882f5a699..1f8d3871b9 100644
--- a/Library/Homebrew/compat.rb
+++ b/Library/Homebrew/compat.rb
@@ -1,32 +1,11 @@
-require "compat/fails_with_llvm"
-require "compat/tap"
 require "compat/hbc"
 require "compat/formula"
-require "compat/formula_specialties"
 require "compat/formula_support"
-require "compat/global"
-require "compat/hardware"
-require "compat/macos"
-require "compat/md5"
-require "compat/sha1"
 require "compat/requirements"
-require "compat/version"
 require "compat/download_strategy"
-require "compat/keg"
-require "compat/pathname"
 require "compat/dependency_collector"
-require "compat/language/haskell"
-require "compat/xcode"
-require "compat/software_spec"
-require "compat/utils"
-require "compat/json"
-require "compat/ARGV"
-require "compat/build_options"
-require "compat/tab"
 require "compat/ENV/shared"
-require "compat/ENV/std"
-require "compat/ENV/super"
-require "compat/utils/shell"
 require "compat/extend/string"
 require "compat/gpg"
 require "compat/dependable"
+require "compat/os/mac"
diff --git a/Library/Homebrew/compat/ARGV.rb b/Library/Homebrew/compat/ARGV.rb
deleted file mode 100644
index e56c4e01fd..0000000000
--- a/Library/Homebrew/compat/ARGV.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-module HomebrewArgvExtension
-  def build_32_bit?
-    odisabled "ARGV.build_32_bit?"
-  end
-end
diff --git a/Library/Homebrew/compat/ENV/shared.rb b/Library/Homebrew/compat/ENV/shared.rb
index 36ee456270..6bca25f9de 100644
--- a/Library/Homebrew/compat/ENV/shared.rb
+++ b/Library/Homebrew/compat/ENV/shared.rb
@@ -1,10 +1,9 @@
 module SharedEnvExtension
   def j1
-    odeprecated "ENV.j1", "ENV.deparallelize"
-    deparallelize
+    odisabled "ENV.j1", "ENV.deparallelize"
   end
 
   def java_cache
-    odeprecated "ENV.java_cache"
+    odisabled "ENV.java_cache"
   end
 end
diff --git a/Library/Homebrew/compat/ENV/std.rb b/Library/Homebrew/compat/ENV/std.rb
deleted file mode 100644
index beca4ed6f4..0000000000
--- a/Library/Homebrew/compat/ENV/std.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-module Stdenv
-  def fast
-    odisabled "ENV.fast"
-  end
-
-  def O4
-    odisabled "ENV.O4"
-  end
-
-  def Og
-    odisabled "ENV.Og"
-  end
-
-  def gcc_4_0_1
-    odisabled "ENV.gcc_4_0_1", "ENV.gcc_4_0"
-  end
-
-  def gcc
-    odisabled "ENV.gcc", "ENV.gcc_4_2"
-  end
-
-  def libpng
-    odisabled "ENV.libpng", "ENV.x11"
-  end
-end
diff --git a/Library/Homebrew/compat/ENV/super.rb b/Library/Homebrew/compat/ENV/super.rb
deleted file mode 100644
index 53a6bdc4d6..0000000000
--- a/Library/Homebrew/compat/ENV/super.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-module Superenv
-  def fast
-    odisabled "ENV.fast"
-  end
-
-  def O4
-    odisabled "ENV.O4"
-  end
-
-  def Og
-    odisabled "ENV.Og"
-  end
-
-  def gcc_4_0_1
-    odisabled "ENV.gcc_4_0_1", "ENV.gcc_4_0"
-  end
-
-  def gcc
-    odisabled "ENV.gcc", "ENV.gcc_4_2"
-  end
-
-  def libxml2
-    odisabled "ENV.libxml2"
-  end
-
-  def minimal_optimization
-    odisabled "ENV.minimal_optimization"
-  end
-
-  def no_optimization
-    odisabled "ENV.no_optimization"
-  end
-
-  def enable_warnings
-    odisabled "ENV.enable_warnings"
-  end
-
-  def macosxsdk
-    odisabled "ENV.macosxsdk"
-  end
-
-  def remove_macosxsdk
-    odisabled "ENV.remove_macosxsdk"
-  end
-end
diff --git a/Library/Homebrew/compat/build_options.rb b/Library/Homebrew/compat/build_options.rb
deleted file mode 100644
index 6e566a08c9..0000000000
--- a/Library/Homebrew/compat/build_options.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-class BuildOptions
-  def build_32_bit?
-    odisabled "build.build_32_bit?"
-  end
-
-  def build_bottle?
-    odisabled "build.build_bottle?", "build.bottle?"
-  end
-end
diff --git a/Library/Homebrew/compat/dependable.rb b/Library/Homebrew/compat/dependable.rb
index faeeb9b183..1b7eec2f0c 100644
--- a/Library/Homebrew/compat/dependable.rb
+++ b/Library/Homebrew/compat/dependable.rb
@@ -1,5 +1,6 @@
 module Dependable
   def run?
+    odeprecated "Dependable#run?"
     tags.include? :run
   end
 end
diff --git a/Library/Homebrew/compat/dependency_collector.rb b/Library/Homebrew/compat/dependency_collector.rb
index 9ee2b14035..685bbaf0ea 100644
--- a/Library/Homebrew/compat/dependency_collector.rb
+++ b/Library/Homebrew/compat/dependency_collector.rb
@@ -9,56 +9,42 @@ class DependencyCollector
 
     def parse_string_spec(spec, tags)
       if (tag = tags.first) && LANGUAGE_MODULES.include?(tag)
-        odeprecated "'depends_on ... => #{tag.inspect}'"
-        LanguageModuleRequirement.new(tag, spec, tags[1])
-      else
-        super
+        odisabled "'depends_on ... => #{tag.inspect}'"
       end
+
+      if tags.include?(:run)
+        odeprecated "'depends_on ... => :run'"
+      end
+
+      super
     end
 
     def parse_symbol_spec(spec, tags)
       case spec
       when :clt
-        odeprecated "'depends_on :clt'"
+        odisabled "'depends_on :clt'"
       when :tex
-        odeprecated "'depends_on :tex'"
-        TeXRequirement.new(tags)
-      when :autoconf, :automake, :bsdmake, :libtool
-        output_deprecation(spec)
-        autotools_dep(spec, tags)
-      when :cairo, :fontconfig, :freetype, :libpng, :pixman
-        output_deprecation(spec)
-        Dependency.new(spec.to_s, tags)
-      when :ant, :expat
-        output_deprecation(spec)
-        Dependency.new(spec.to_s, tags)
+        odisabled "'depends_on :tex'"
       when :libltdl
-        output_deprecation("libtool")
-        Dependency.new("libtool", tags)
+        output_disabled(spec, "libtool")
       when :apr
-        output_deprecation(spec, "apr-util")
-        Dependency.new("apr-util", tags)
+        output_disabled(spec, "apr-util")
       when :fortran
-        output_deprecation(spec, "gcc")
-        Dependency.new("gcc", tags)
+        output_disabled(spec, "gcc")
       when :gpg
-        output_deprecation(spec, "gnupg")
-        Dependency.new("gnupg", tags)
+        output_disabled(spec, "gnupg")
       when :hg
-        output_deprecation(spec, "mercurial")
-        Dependency.new("mercurial", tags)
+        output_disabled(spec, "mercurial")
       when :mpi
-        output_deprecation(spec, "open-mpi")
-        Dependency.new("open-mpi", tags)
+        output_disabled(spec, "open-mpi")
       when :python, :python2
-        output_deprecation(spec, "python@2")
-        Dependency.new("python@2", tags)
+        output_disabled(spec, "python@2")
       when :python3
-        output_deprecation(spec, "python")
-        Dependency.new("python", tags)
-      when :emacs, :mysql, :perl, :postgresql, :rbenv, :ruby
-        output_deprecation(spec)
-        Dependency.new(spec.to_s, tags)
+        output_disabled(spec, "python")
+      when :ant, :autoconf, :automake, :bsdmake, :cairo, :emacs, :expat,
+           :fontconfig, :freetype, :libtool, :libpng, :mysql, :perl, :pixman,
+           :postgresql, :rbenv, :ruby
+        output_disabled(spec)
       else
         super
       end
@@ -66,14 +52,9 @@ class DependencyCollector
 
     private
 
-    def autotools_dep(spec, tags)
-      tags << :build
-      Dependency.new(spec.to_s, tags)
-    end
-
-    def output_deprecation(dependency, new_dependency = dependency)
-      odeprecated "'depends_on :#{dependency}'",
-                  "'depends_on \"#{new_dependency}\"'"
+    def output_disabled(dependency, new_dependency = dependency)
+      odisabled "'depends_on :#{dependency}'",
+                "'depends_on \"#{new_dependency}\"'"
     end
   end
 
diff --git a/Library/Homebrew/compat/extend/string.rb b/Library/Homebrew/compat/extend/string.rb
index 9d1f665576..b704cd2b5f 100644
--- a/Library/Homebrew/compat/extend/string.rb
+++ b/Library/Homebrew/compat/extend/string.rb
@@ -1,7 +1,7 @@
 class String
   def undent
-    odeprecated "<<-EOS.undent", "<<~EOS"
-    gsub(/^[ \t]{#{(slice(/^[ \t]+/) || '').length}}/, "")
+    odisabled "<<-EOS.undent", "<<~EOS"
+    self
   end
   alias unindent undent
 
diff --git a/Library/Homebrew/compat/fails_with_llvm.rb b/Library/Homebrew/compat/fails_with_llvm.rb
deleted file mode 100644
index 47bda4e0b3..0000000000
--- a/Library/Homebrew/compat/fails_with_llvm.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-class Formula
-  def fails_with_llvm(_msg = nil, _data = nil)
-    odisabled "Formula#fails_with_llvm in install"
-  end
-
-  def self.fails_with_llvm(_msg = nil, _data = {})
-    odisabled "Formula.fails_with_llvm"
-  end
-end
diff --git a/Library/Homebrew/compat/formula.rb b/Library/Homebrew/compat/formula.rb
index 6f740710d8..397b8e12ca 100644
--- a/Library/Homebrew/compat/formula.rb
+++ b/Library/Homebrew/compat/formula.rb
@@ -1,74 +1,5 @@
-module FormulaCompat
-  def x11_installed?
-    odisabled "Formula#x11_installed?", "MacOS::X11.installed?"
-  end
-
-  def snow_leopard_64?
-    odisabled "Formula#snow_leopard_64?", "MacOS.prefer_64_bit?"
-  end
-end
-
 class Formula
-  include FormulaCompat
-  extend FormulaCompat
-
-  def std_cmake_parameters
-    odisabled "Formula#std_cmake_parameters", "Formula#std_cmake_args"
-  end
-
-  def cxxstdlib_check(_)
-    odisabled "Formula#cxxstdlib_check in install",
-              "Formula.cxxstdlib_check outside install"
-  end
-
-  def self.bottle_sha1(*)
-    odisabled "Formula.bottle_sha1"
-  end
-
-  def self.all
-    odisabled "Formula.all", "Formula.map"
-  end
-
-  def self.canonical_name(_)
-    odisabled "Formula.canonical_name", "Formulary.canonical_name"
-  end
-
-  def self.class_s(_)
-    odisabled "Formula.class_s", "Formulary.class_s"
-  end
-
-  def self.factory(_)
-    odisabled "Formula.factory", "Formulary.factory"
-  end
-
-  def self.require_universal_deps
-    odisabled "Formula.require_universal_deps"
-  end
-
-  def self.path(_)
-    odisabled "Formula.path", "Formulary.core_path"
-  end
-
-  DATA = :DATA
-
-  def patches
-    # Don't print deprecation warning because this method is inherited
-    # when used.
-    {}
-  end
-
-  def python(_options = {}, &_)
-    odisabled "Formula#python"
-  end
-  alias python2 python
-  alias python3 python
-
-  def startup_plist
-    odisabled "Formula#startup_plist", "Formula#plist"
-  end
-
-  def rake(*args)
-    odeprecated "FileUtils#rake", "system \"rake\""
-    system "rake", *args
+  def rake(*)
+    odisabled "FileUtils#rake", "system \"rake\""
   end
 end
diff --git a/Library/Homebrew/compat/formula_specialties.rb b/Library/Homebrew/compat/formula_specialties.rb
deleted file mode 100644
index bc4d20beab..0000000000
--- a/Library/Homebrew/compat/formula_specialties.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-class ScriptFileFormula < Formula
-  def install
-    odisabled "ScriptFileFormula#install", "Formula#install"
-  end
-end
-
-class GithubGistFormula < ScriptFileFormula
-  def self.url(_val)
-    odisabled "GithubGistFormula.url", "Formula.url"
-  end
-end
-
-class AmazonWebServicesFormula < Formula
-  def install
-    odisabled "AmazonWebServicesFormula#install", "Formula#install"
-  end
-  alias standard_install install
-
-  # Use this method to generate standard caveats.
-  def standard_instructions(_, _)
-    odisabled "AmazonWebServicesFormula#standard_instructions", "Formula#caveats"
-  end
-end
diff --git a/Library/Homebrew/compat/formula_support.rb b/Library/Homebrew/compat/formula_support.rb
index 9cb8d8ff14..81c37f313d 100644
--- a/Library/Homebrew/compat/formula_support.rb
+++ b/Library/Homebrew/compat/formula_support.rb
@@ -2,17 +2,80 @@ require "formula_support"
 
 class KegOnlyReason
   module Compat
+    def valid?
+      case @reason
+      when :provided_by_osx
+        odisabled "keg_only :provided_by_osx", "keg_only :provided_by_macos"
+      when :shadowed_by_osx
+        odisabled "keg_only :shadowed_by_osx", "keg_only :shadowed_by_macos"
+      when :provided_pre_mountain_lion
+        odeprecated "keg_only :provided_pre_mountain_lion"
+        MacOS.version < :mountain_lion
+      when :provided_pre_mavericks
+        odeprecated "keg_only :provided_pre_mavericks"
+        MacOS.version < :mavericks
+      when :provided_pre_el_capitan
+        odeprecated "keg_only :provided_pre_el_capitan"
+        MacOS.version < :el_capitan
+      when :provided_pre_high_sierra
+        odeprecated "keg_only :provided_pre_high_sierra"
+        MacOS.version < :high_sierra
+      when :provided_until_xcode43
+        odeprecated "keg_only :provided_until_xcode43"
+        MacOS::Xcode.version < "4.3"
+      when :provided_until_xcode5
+        odeprecated "keg_only :provided_until_xcode5"
+        MacOS::Xcode.version < "5.0"
+      else
+        super
+      end
+    end
+
     def to_s
       case @reason
       when :provided_by_osx
-        odeprecated "keg_only :provided_by_osx", "keg_only :provided_by_macos"
-        @reason = :provided_by_macos
+        odisabled "keg_only :provided_by_osx", "keg_only :provided_by_macos"
       when :shadowed_by_osx
-        odeprecated "keg_only :shadowed_by_osx", "keg_only :shadowed_by_macos"
-        @reason = :shadowed_by_macos
-      end
+        odisabled "keg_only :shadowed_by_osx", "keg_only :shadowed_by_macos"
+      when :provided_pre_mountain_lion
+        odeprecated "keg_only :provided_pre_mountain_lion"
 
-      super
+        <<~EOS
+          macOS already provides this software in versions before Mountain Lion
+        EOS
+      when :provided_pre_mavericks
+        odeprecated "keg_only :provided_pre_mavericks"
+
+        <<~EOS
+          macOS already provides this software in versions before Mavericks
+        EOS
+      when :provided_pre_el_capitan
+        odeprecated "keg_only :provided_pre_el_capitan"
+
+        <<~EOS
+          macOS already provides this software in versions before El Capitan
+        EOS
+      when :provided_pre_high_sierra
+        odeprecated "keg_only :provided_pre_high_sierra"
+
+        <<~EOS
+          macOS already provides this software in versions before High Sierra
+        EOS
+      when :provided_until_xcode43
+        odeprecated "keg_only :provided_until_xcode43"
+
+        <<~EOS
+          Xcode provides this software prior to version 4.3
+        EOS
+      when :provided_until_xcode5
+        odeprecated "keg_only :provided_until_xcode5"
+
+        <<~EOS
+          Xcode provides this software prior to version 5
+        EOS
+      else
+        super
+      end.to_s.strip
     end
   end
 
diff --git a/Library/Homebrew/compat/global.rb b/Library/Homebrew/compat/global.rb
deleted file mode 100644
index 9c8f0624cc..0000000000
--- a/Library/Homebrew/compat/global.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-module Homebrew
-  module_function
-
-  def method_missing(method, *args, &block)
-    if instance_methods.include?(method)
-      odisabled "#{self}##{method}", "'module_function' or 'def self.#{method}' to convert it to a class method"
-    end
-    super
-  end
-
-  def respond_to_missing?(method, include_private = false)
-    return true if method_defined?(method)
-    super(method, include_private)
-  end
-end
diff --git a/Library/Homebrew/compat/gpg.rb b/Library/Homebrew/compat/gpg.rb
index e802d939cf..5aaecf4d31 100644
--- a/Library/Homebrew/compat/gpg.rb
+++ b/Library/Homebrew/compat/gpg.rb
@@ -1,27 +1,24 @@
-require "utils"
 
 module Gpg
   module_function
 
   def executable
-    odeprecated "Gpg.executable", 'which "gpg"'
-    which "gpg"
+    odisabled "Gpg.executable", 'which "gpg"'
   end
 
   def available?
-    odeprecated "Gpg.available?", 'which "gpg"'
-    File.executable?(executable.to_s)
+    odisabled "Gpg.available?", 'which "gpg"'
   end
 
   def create_test_key(_)
-    odeprecated "Gpg.create_test_key"
+    odisabled "Gpg.create_test_key"
   end
 
   def cleanup_test_processes!
-    odeprecated "Gpg.cleanup_test_processes!"
+    odisabled "Gpg.cleanup_test_processes!"
   end
 
   def test(_)
-    odeprecated "Gpg.test"
+    odisabled "Gpg.test"
   end
 end
diff --git a/Library/Homebrew/compat/hardware.rb b/Library/Homebrew/compat/hardware.rb
deleted file mode 100644
index 28bc79c60d..0000000000
--- a/Library/Homebrew/compat/hardware.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-module Hardware
-  class << self
-    def is_32_bit?
-      odisabled "Hardware.is_32_bit?", "Hardware::CPU.is_32_bit?"
-    end
-
-    def is_64_bit?
-      odisabled "Hardware.is_64_bit?", "Hardware::CPU.is_64_bit?"
-    end
-
-    def bits
-      odisabled "Hardware.bits", "Hardware::CPU.bits"
-    end
-
-    def cpu_type
-      odisabled "Hardware.cpu_type", "Hardware::CPU.type"
-    end
-
-    def cpu_family
-      odisabled "Hardware.cpu_family", "Hardware::CPU.family"
-    end
-
-    def intel_family
-      odisabled "Hardware.intel_family", "Hardware::CPU.family"
-    end
-
-    def ppc_family
-      odisabled "Hardware.ppc_family", "Hardware::CPU.family"
-    end
-
-    def processor_count
-      odisabled "Hardware.processor_count", "Hardware::CPU.cores"
-    end
-  end
-end
diff --git a/Library/Homebrew/compat/json.rb b/Library/Homebrew/compat/json.rb
deleted file mode 100644
index 18763b8a6e..0000000000
--- a/Library/Homebrew/compat/json.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require "json"
-
-module Utils
-  module JSON
-    module_function
-
-    def load(_)
-      odisabled "Utils::JSON.load", "JSON.parse"
-    end
-
-    def dump(_)
-      odisabled "Utils::JSON.dump", "JSON.generate"
-    end
-
-    def stringify_keys(_)
-      odisabled "Utils::JSON.stringify_keys"
-    end
-  end
-end
diff --git a/Library/Homebrew/compat/keg.rb b/Library/Homebrew/compat/keg.rb
deleted file mode 100644
index 81e1cf0b3f..0000000000
--- a/Library/Homebrew/compat/keg.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class Keg
-  def fname
-    odisabled "Keg#fname", "Keg#name"
-  end
-end
diff --git a/Library/Homebrew/compat/language/haskell.rb b/Library/Homebrew/compat/language/haskell.rb
deleted file mode 100644
index 8e50598743..0000000000
--- a/Library/Homebrew/compat/language/haskell.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-module Language
-  module Haskell
-    module Cabal
-      def cabal_clean_lib
-        odisabled "Language::Haskell::Cabal#cabal_clean_lib"
-      end
-    end
-  end
-end
diff --git a/Library/Homebrew/compat/macos.rb b/Library/Homebrew/compat/macos.rb
deleted file mode 100644
index 879af83571..0000000000
--- a/Library/Homebrew/compat/macos.rb
+++ /dev/null
@@ -1,124 +0,0 @@
-require "development_tools"
-
-if OS.mac?
-  MACOS_FULL_VERSION = OS::Mac.full_version.to_s.freeze
-  MACOS_VERSION = OS::Mac.version.to_s.freeze
-end
-
-module OS
-  module Mac
-    module_function
-
-    def xcode_folder
-      odisabled "MacOS.xcode_folder", "MacOS::Xcode.folder"
-    end
-
-    def xcode_prefix
-      odisabled "MacOS.xcode_prefix", "MacOS::Xcode.prefix"
-    end
-
-    def xcode_installed?
-      odisabled "MacOS.xcode_installed?", "MacOS::Xcode.installed?"
-    end
-
-    def xcode_version
-      odisabled "MacOS.xcode_version", "MacOS::Xcode.version"
-    end
-
-    def clt_installed?
-      odisabled "MacOS.clt_installed?", "MacOS::CLT.installed?"
-    end
-
-    def clt_version?
-      odisabled "MacOS.clt_version?", "MacOS::CLT.version"
-    end
-
-    def x11_installed?
-      odisabled "MacOS.x11_installed?", "MacOS::X11.installed?"
-    end
-
-    def x11_prefix
-      odisabled "MacOS.x11_prefix", "MacOS::X11.prefix"
-    end
-
-    def leopard?
-      odisabled "MacOS.leopard?", "'MacOS.version == :leopard'"
-    end
-
-    def snow_leopard?
-      odisabled "MacOS.snow_leopard?", "'MacOS.version >= :snow_leopard'"
-    end
-
-    def snow_leopard_or_newer?
-      odisabled "MacOS.snow_leopard_or_newer?", "'MacOS.version >= :snow_leopard'"
-    end
-
-    def lion?
-      odisabled "MacOS.lion?", "'MacOS.version >= :lion'"
-    end
-
-    def lion_or_newer?
-      odisabled "MacOS.lion_or_newer?", "'MacOS.version >= :lion'"
-    end
-
-    def mountain_lion?
-      odisabled "MacOS.mountain_lion?", "'MacOS.version >= :mountain_lion'"
-    end
-
-    def mountain_lion_or_newer?
-      odisabled "MacOS.mountain_lion_or_newer?", "'MacOS.version >= :mountain_lion'"
-    end
-
-    def macports_or_fink_installed?
-      odisabled "MacOS.macports_or_fink_installed?", "!MacOS.macports_or_fink.empty?"
-    end
-
-    def locate(_)
-      odisabled "MacOS.locate", "DevelopmentTools.locate"
-    end
-
-    def default_cc
-      odisabled "MacOS.default_cc", "DevelopmentTools.default_cc"
-    end
-
-    def default_compiler
-      odisabled "MacOS.default_compiler", "DevelopmentTools.default_compiler"
-    end
-
-    def gcc_40_build_version
-      odisabled "MacOS.gcc_40_build_version", "DevelopmentTools.gcc_4_0_build_version"
-    end
-
-    def gcc_4_0_build_version
-      odisabled "MacOS.gcc_4_0_build_version", "DevelopmentTools.gcc_4_0_build_version"
-    end
-
-    def gcc_42_build_version
-      odisabled "MacOS.gcc_42_build_version", "DevelopmentTools.gcc_4_2_build_version"
-    end
-
-    def gcc_build_version
-      odisabled "MacOS.gcc_build_version", "DevelopmentTools.gcc_4_2_build_version"
-    end
-
-    def llvm_build_version
-      odisabled "MacOS.llvm_build_version"
-    end
-
-    def clang_version
-      odisabled "MacOS.clang_version", "DevelopmentTools.clang_version"
-    end
-
-    def clang_build_version
-      odisabled "MacOS.clang_build_version", "DevelopmentTools.clang_build_version"
-    end
-
-    def has_apple_developer_tools?
-      odisabled "MacOS.has_apple_developer_tools?", "DevelopmentTools.installed?"
-    end
-
-    def release
-      odisabled "MacOS.release", "MacOS.version"
-    end
-  end
-end
diff --git a/Library/Homebrew/compat/md5.rb b/Library/Homebrew/compat/md5.rb
deleted file mode 100644
index ede7edecb8..0000000000
--- a/Library/Homebrew/compat/md5.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-class Formula
-  def self.md5(_val)
-    odisabled "Formula.md5", "Formula.sha256"
-  end
-end
-
-class SoftwareSpec
-  def md5(_val)
-    odisabled "SoftwareSpec#md5", "SoftwareSpec#sha256"
-  end
-end
-
-class Resource
-  def md5(_val)
-    odisabled "Resource#md5", "Resource#sha256"
-  end
-end
-
-class Pathname
-  def md5
-    odisabled "Pathname#md5", "Pathname#sha256"
-  end
-end
diff --git a/Library/Homebrew/compat/os/mac.rb b/Library/Homebrew/compat/os/mac.rb
new file mode 100644
index 0000000000..6806fe900a
--- /dev/null
+++ b/Library/Homebrew/compat/os/mac.rb
@@ -0,0 +1,10 @@
+module OS
+  module Mac
+    class << self
+      def release
+        odeprecated "MacOS.release", "MacOS.version"
+        version
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/compat/pathname.rb b/Library/Homebrew/compat/pathname.rb
deleted file mode 100644
index df4b261a91..0000000000
--- a/Library/Homebrew/compat/pathname.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-class Pathname
-  def cp(_)
-    odisabled "Pathname#cp", "FileUtils.cp"
-  end
-
-  def chmod_R(_)
-    odisabled "Pathname#chmod_R", "FileUtils.chmod_R"
-  end
-end
diff --git a/Library/Homebrew/compat/requirements.rb b/Library/Homebrew/compat/requirements.rb
index 3dd5c74795..af0a9a25d0 100644
--- a/Library/Homebrew/compat/requirements.rb
+++ b/Library/Homebrew/compat/requirements.rb
@@ -1,123 +1,107 @@
 require "requirements"
-require "compat/requirements/language_module_requirement"
 
 class CVSRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("CVSRequirement", "'depends_on \"cvs\"'")
-    which "cvs"
+    odisabled("CVSRequirement", "'depends_on \"cvs\"'")
   end
 end
 
 class EmacsRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("EmacsRequirement", "'depends_on \"emacs\"'")
-    which "emacs"
+    odisabled("EmacsRequirement", "'depends_on \"emacs\"'")
   end
 end
 
 class FortranRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("FortranRequirement", "'depends_on \"gcc\"'")
-    which "gfortran"
+    odisabled("FortranRequirement", "'depends_on \"gcc\"'")
   end
 end
 
 class GitRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("GitRequirement", "'depends_on \"git\"'")
-    which "git"
+    odisabled("GitRequirement", "'depends_on \"git\"'")
   end
 end
 
 class GPG2Requirement < Requirement
   fatal true
   satisfy do
-    odeprecated("GPG2Requirement", "'depends_on \"gnupg\"'")
-    which "gpg"
+    odisabled("GPG2Requirement", "'depends_on \"gnupg\"'")
   end
 end
 
 class MercurialRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("MercurialRequirement", "'depends_on \"mercurial\"'")
-    which "hg"
+    odisabled("MercurialRequirement", "'depends_on \"mercurial\"'")
   end
 end
 
 class MPIRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("MPIRequirement", "'depends_on \"open-mpi\"'")
-    which "mpicc"
+    odisabled("MPIRequirement", "'depends_on \"open-mpi\"'")
   end
 end
 
 class MysqlRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("MysqlRequirement", "'depends_on \"mysql\"'")
-    which "mysql_config"
+    odisabled("MysqlRequirement", "'depends_on \"mysql\"'")
   end
 end
 
 class PerlRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("PerlRequirement", "'depends_on \"perl\"'")
-    which "perl"
+    odisabled("PerlRequirement", "'depends_on \"perl\"'")
   end
 end
 
 class PostgresqlRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("PostgresqlRequirement", "'depends_on \"postgresql\"'")
-    which "pg_config"
+    odisabled("PostgresqlRequirement", "'depends_on \"postgresql\"'")
   end
 end
 
 class PythonRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("PythonRequirement", "'depends_on \"python@2\"'")
-    which "python2"
+    odisabled("PythonRequirement", "'depends_on \"python@2\"'")
   end
 end
 
 class Python3Requirement < Requirement
   fatal true
   satisfy do
-    odeprecated("Python3Requirement", "'depends_on \"python\"'")
-    which "python"
+    odisabled("Python3Requirement", "'depends_on \"python\"'")
   end
 end
 
 class RbenvRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("RbenvRequirement", "'depends_on \"rbenv\"'")
-    which "rbenv"
+    odisabled("RbenvRequirement", "'depends_on \"rbenv\"'")
   end
 end
 
 class RubyRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("RubyRequirement", "'depends_on \"ruby\"'")
-    which "ruby"
+    odisabled("RubyRequirement", "'depends_on \"ruby\"'")
   end
 end
 
 class SubversionRequirement < Requirement
   fatal true
   satisfy do
-    odeprecated("SubversionRequirement", "'depends_on \"subversion\"'")
-    which "svn"
+    odisabled("SubversionRequirement", "'depends_on \"subversion\"'")
   end
 end
 
@@ -126,8 +110,7 @@ class TeXRequirement < Requirement
   cask "mactex"
   download "https://www.tug.org/mactex/"
   satisfy do
-    odeprecated("TeXRequirement")
-    which("tex") || which("latex")
+    odisabled("TeXRequirement")
   end
 end
 
diff --git a/Library/Homebrew/compat/requirements/language_module_requirement.rb b/Library/Homebrew/compat/requirements/language_module_requirement.rb
deleted file mode 100644
index fc9dcc4428..0000000000
--- a/Library/Homebrew/compat/requirements/language_module_requirement.rb
+++ /dev/null
@@ -1,63 +0,0 @@
-require "requirement"
-
-class LanguageModuleRequirement < Requirement
-  fatal true
-
-  def initialize(language, module_name, import_name = nil)
-    @language = language
-    @module_name = module_name
-    @import_name = import_name || module_name
-    super([language, module_name, import_name])
-  end
-
-  satisfy(build_env: false) { quiet_system(*the_test) }
-
-  def message
-    s = <<~EOS
-      Unsatisfied dependency: #{@module_name}
-      Homebrew does not provide special #{@language.to_s.capitalize} dependencies; install with:
-        `#{command_line} #{@module_name}`
-    EOS
-
-    unless [:python, :perl, :ruby].include? @language
-      s += <<~EOS
-        You may need to: `brew install #{@language}`
-
-      EOS
-    end
-
-    s
-  end
-
-  def the_test
-    case @language
-    when :lua
-      ["/usr/bin/env", "luarocks-5.2", "show", @import_name.to_s]
-    when :lua51
-      ["/usr/bin/env", "luarocks-5.1", "show", @import_name.to_s]
-    when :perl
-      ["/usr/bin/env", "perl", "-e", "use #{@import_name}"]
-    when :python
-      ["/usr/bin/env", "python2", "-c", "import #{@import_name}"]
-    when :python3
-      ["/usr/bin/env", "python", "-c", "import #{@import_name}"]
-    when :ruby
-      ["/usr/bin/env", "ruby", "-rubygems", "-e", "require '#{@import_name}'"]
-    end
-  end
-
-  def command_line
-    case @language
-    when :lua     then "luarocks-5.2 install"
-    when :lua51   then "luarocks-5.1 install"
-    when :perl    then "cpan -i"
-    when :python  then "pip3 install"
-    when :python3 then "pip install"
-    when :ruby    then "gem install"
-    end
-  end
-
-  def display_s
-    "#{@module_name} (#{@language} module)"
-  end
-end
diff --git a/Library/Homebrew/compat/sha1.rb b/Library/Homebrew/compat/sha1.rb
deleted file mode 100644
index adf11bdd5c..0000000000
--- a/Library/Homebrew/compat/sha1.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-class Formula
-  def self.sha1(_val)
-    odisabled "Formula.sha1", "Formula.sha256"
-  end
-end
-
-class SoftwareSpec
-  def sha1(_val)
-    odisabled "SoftwareSpec#sha1", "SoftwareSpec#sha256"
-  end
-end
-
-class Resource
-  def sha1(_val)
-    odisabled "Resource#sha1", "Resource#sha256"
-  end
-end
-
-class BottleSpecification
-  def sha1(_val)
-    odisabled "BottleSpecification#sha1", "BottleSpecification#sha256"
-  end
-end
-
-class Pathname
-  def sha1
-    odisabled "Pathname#sha1", "Pathname#sha256"
-  end
-end
diff --git a/Library/Homebrew/compat/software_spec.rb b/Library/Homebrew/compat/software_spec.rb
deleted file mode 100644
index 814c00fa88..0000000000
--- a/Library/Homebrew/compat/software_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class BottleSpecification
-  def revision(*)
-    odisabled "BottleSpecification.revision", "BottleSpecification.rebuild"
-  end
-end
diff --git a/Library/Homebrew/compat/tab.rb b/Library/Homebrew/compat/tab.rb
deleted file mode 100644
index 651bcf1e19..0000000000
--- a/Library/Homebrew/compat/tab.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class Tab < OpenStruct
-  def build_32_bit?
-    odisabled "Tab.build_32_bit?"
-  end
-end
diff --git a/Library/Homebrew/compat/tap.rb b/Library/Homebrew/compat/tap.rb
deleted file mode 100644
index a1e3ce1727..0000000000
--- a/Library/Homebrew/compat/tap.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require "tap"
-
-class Tap
-  def core_formula_repository?
-    odisabled "Tap#core_formula_repository?", "Tap#core_tap?"
-  end
-end
diff --git a/Library/Homebrew/compat/utils.rb b/Library/Homebrew/compat/utils.rb
deleted file mode 100644
index f83d075998..0000000000
--- a/Library/Homebrew/compat/utils.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-module Tty
-  module_function
-
-  def white
-    odisabled "Tty.white", "Tty.reset.bold"
-  end
-end
-
-def puts_columns(_)
-  odisabled "puts_columns", "puts Formatter.columns"
-end
-
-def plural(_, _)
-  odisabled "#plural", "Formatter.pluralize"
-end
diff --git a/Library/Homebrew/compat/utils/shell.rb b/Library/Homebrew/compat/utils/shell.rb
deleted file mode 100644
index 2f387d967b..0000000000
--- a/Library/Homebrew/compat/utils/shell.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-module Utils
-  module Shell
-    def self.shell_profile
-      odisabled "Utils::Shell.shell_profile", "Utils::Shell.profile"
-    end
-  end
-end
diff --git a/Library/Homebrew/compat/version.rb b/Library/Homebrew/compat/version.rb
deleted file mode 100644
index 4a6fd7ace5..0000000000
--- a/Library/Homebrew/compat/version.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-class Version
-  def slice(*)
-    odisabled "Version#slice", "Version#to_s.slice"
-  end
-end
diff --git a/Library/Homebrew/compat/xcode.rb b/Library/Homebrew/compat/xcode.rb
deleted file mode 100644
index f212ada641..0000000000
--- a/Library/Homebrew/compat/xcode.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-module OS
-  module Mac
-    module Xcode
-      module_function
-
-      def provides_autotools?
-        odisabled "OS::Mac::Xcode.provides_autotools?"
-      end
-    end
-  end
-end
diff --git a/Library/Homebrew/config.rb b/Library/Homebrew/config.rb
index 30b7bc6c9c..38d7c80438 100644
--- a/Library/Homebrew/config.rb
+++ b/Library/Homebrew/config.rb
@@ -2,8 +2,6 @@ unless ENV["HOMEBREW_BREW_FILE"]
   raise "HOMEBREW_BREW_FILE was not exported! Please call bin/brew directly!"
 end
 
-require "constants"
-
 # Path to `bin/brew` main executable in HOMEBREW_PREFIX
 HOMEBREW_BREW_FILE = Pathname.new(ENV["HOMEBREW_BREW_FILE"])
 
diff --git a/Library/Homebrew/constants.rb b/Library/Homebrew/constants.rb
index 3d2a1d0f39..25326075e5 100644
--- a/Library/Homebrew/constants.rb
+++ b/Library/Homebrew/constants.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 # RuboCop version used for `brew style` and `brew cask style`
-HOMEBREW_RUBOCOP_VERSION = "0.54.0"
-HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.18.0" # has to be updated when RuboCop version changes
+HOMEBREW_RUBOCOP_VERSION = "0.55.0"
+HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.19.0" # has to be updated when RuboCop version changes
diff --git a/Library/Homebrew/dependency_collector.rb b/Library/Homebrew/dependency_collector.rb
index 74f42a6aaf..1a00c72012 100644
--- a/Library/Homebrew/dependency_collector.rb
+++ b/Library/Homebrew/dependency_collector.rb
@@ -2,7 +2,6 @@ require "dependency"
 require "dependencies"
 require "requirement"
 require "requirements"
-require "set"
 require "extend/cachable"
 
 ## A dependency is a formula that another formula needs to install.
diff --git a/Library/Homebrew/descriptions.rb b/Library/Homebrew/descriptions.rb
index bc19826731..4db47e77f1 100644
--- a/Library/Homebrew/descriptions.rb
+++ b/Library/Homebrew/descriptions.rb
@@ -1,4 +1,3 @@
-require "set"
 require "formula"
 require "formula_versions"
 
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 5eaffe2afa..45c9561c62 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -39,11 +39,9 @@
 
 require "formula"
 require "formula_versions"
-require "utils"
 require "utils/curl"
 require "extend/ENV"
 require "formula_cellar_checks"
-require "official_taps"
 require "cmd/search"
 require "cmd/style"
 require "date"
@@ -141,826 +139,834 @@ module Homebrew
 
     ofail "#{Formatter.pluralize(problem_count, "problem")} in #{Formatter.pluralize(formula_count, "formula")}"
   end
-end
 
-class FormulaText
-  def initialize(path)
-    @text = path.open("rb", &:read)
-    @lines = @text.lines.to_a
-  end
+  class FormulaText
+    def initialize(path)
+      @text = path.open("rb", &:read)
+      @lines = @text.lines.to_a
+    end
 
-  def without_patch
-    @text.split("\n__END__").first
-  end
+    def without_patch
+      @text.split("\n__END__").first
+    end
 
-  def data?
-    /^[^#]*\bDATA\b/ =~ @text
-  end
+    def data?
+      /^[^#]*\bDATA\b/ =~ @text
+    end
 
-  def end?
-    /^__END__$/ =~ @text
-  end
+    def end?
+      /^__END__$/ =~ @text
+    end
 
-  def trailing_newline?
-    /\Z\n/ =~ @text
-  end
+    def trailing_newline?
+      /\Z\n/ =~ @text
+    end
 
-  def =~(other)
-    other =~ @text
-  end
+    def =~(other)
+      other =~ @text
+    end
 
-  def include?(s)
-    @text.include? s
-  end
+    def include?(s)
+      @text.include? s
+    end
 
-  def line_number(regex, skip = 0)
-    index = @lines.drop(skip).index { |line| line =~ regex }
-    index ? index + 1 : nil
-  end
+    def line_number(regex, skip = 0)
+      index = @lines.drop(skip).index { |line| line =~ regex }
+      index ? index + 1 : nil
+    end
 
-  def reverse_line_number(regex)
-    index = @lines.reverse.index { |line| line =~ regex }
-    index ? @lines.count - index : nil
-  end
-end
-
-class FormulaAuditor
-  include FormulaCellarChecks
-
-  attr_reader :formula, :text, :problems
-
-  def initialize(formula, options = {})
-    @formula = formula
-    @new_formula = options[:new_formula]
-    @strict = options[:strict]
-    @online = options[:online]
-    @display_cop_names = options[:display_cop_names]
-    @only = options[:only]
-    @except = options[:except]
-    # Accept precomputed style offense results, for efficiency
-    @style_offenses = options[:style_offenses]
-    # Allow the actual official-ness of a formula to be overridden, for testing purposes
-    @official_tap = formula.tap&.official? || options[:official_tap]
-    @problems = []
-    @text = FormulaText.new(formula.path)
-    @specs = %w[stable devel head].map { |s| formula.send(s) }.compact
-  end
-
-  def audit_style
-    return unless @style_offenses
-    @style_offenses.each do |offense|
-      problem offense.to_s(display_cop_name: @display_cop_names)
+    def reverse_line_number(regex)
+      index = @lines.reverse.index { |line| line =~ regex }
+      index ? @lines.count - index : nil
     end
   end
 
-  def audit_file
-    # Under normal circumstances (umask 0022), we expect a file mode of 644. If
-    # the user's umask is more restrictive, respect that by masking out the
-    # corresponding bits. (The also included 0100000 flag means regular file.)
-    wanted_mode = 0100644 & ~File.umask
-    actual_mode = formula.path.stat.mode
-    unless actual_mode == wanted_mode
-      problem format("Incorrect file permissions (%03o): chmod %03o %s",
-                     actual_mode & 0777, wanted_mode & 0777, formula.path)
+  class FormulaAuditor
+    include FormulaCellarChecks
+
+    attr_reader :formula, :text, :problems
+
+    def initialize(formula, options = {})
+      @formula = formula
+      @new_formula = options[:new_formula]
+      @strict = options[:strict]
+      @online = options[:online]
+      @display_cop_names = options[:display_cop_names]
+      @only = options[:only]
+      @except = options[:except]
+      # Accept precomputed style offense results, for efficiency
+      @style_offenses = options[:style_offenses]
+      # Allow the actual official-ness of a formula to be overridden, for testing purposes
+      @official_tap = formula.tap&.official? || options[:official_tap]
+      @problems = []
+      @text = FormulaText.new(formula.path)
+      @specs = %w[stable devel head].map { |s| formula.send(s) }.compact
     end
 
-    problem "'DATA' was found, but no '__END__'" if text.data? && !text.end?
-
-    if text.end? && !text.data?
-      problem "'__END__' was found, but 'DATA' is not used"
+    def audit_style
+      return unless @style_offenses
+      @style_offenses.each do |offense|
+        problem offense.to_s(display_cop_name: @display_cop_names)
+      end
     end
 
-    if text =~ /inreplace [^\n]* do [^\n]*\n[^\n]*\.gsub![^\n]*\n\ *end/m
-      problem "'inreplace ... do' was used for a single substitution (use the non-block form instead)."
-    end
+    def audit_file
+      # Under normal circumstances (umask 0022), we expect a file mode of 644. If
+      # the user's umask is more restrictive, respect that by masking out the
+      # corresponding bits. (The also included 0100000 flag means regular file.)
+      wanted_mode = 0100644 & ~File.umask
+      actual_mode = formula.path.stat.mode
+      unless actual_mode == wanted_mode
+        problem format("Incorrect file permissions (%03o): chmod %03o %s",
+                       actual_mode & 0777, wanted_mode & 0777, formula.path)
+      end
 
-    problem "File should end with a newline" unless text.trailing_newline?
+      problem "'DATA' was found, but no '__END__'" if text.data? && !text.end?
 
-    if formula.versioned_formula?
-      unversioned_formula = begin
-        # build this ourselves as we want e.g. homebrew/core to be present
-        full_name = if formula.tap
-          "#{formula.tap}/#{formula.name}"
-        else
-          formula.name
+      if text.end? && !text.data?
+        problem "'__END__' was found, but 'DATA' is not used"
+      end
+
+      if text =~ /inreplace [^\n]* do [^\n]*\n[^\n]*\.gsub![^\n]*\n\ *end/m
+        problem "'inreplace ... do' was used for a single substitution (use the non-block form instead)."
+      end
+
+      problem "File should end with a newline" unless text.trailing_newline?
+
+      if formula.versioned_formula?
+        unversioned_formula = begin
+          # build this ourselves as we want e.g. homebrew/core to be present
+          full_name = if formula.tap
+            "#{formula.tap}/#{formula.name}"
+          else
+            formula.name
+          end
+          Formulary.factory(full_name.gsub(/@.*$/, "")).path
+        rescue FormulaUnavailableError, TapFormulaAmbiguityError,
+               TapFormulaWithOldnameAmbiguityError
+          Pathname.new formula.path.to_s.gsub(/@.*\.rb$/, ".rb")
         end
-        Formulary.factory(full_name.gsub(/@.*$/, "")).path
-      rescue FormulaUnavailableError, TapFormulaAmbiguityError,
-             TapFormulaWithOldnameAmbiguityError
-        Pathname.new formula.path.to_s.gsub(/@.*\.rb$/, ".rb")
-      end
-      unless unversioned_formula.exist?
-        unversioned_name = unversioned_formula.basename(".rb")
-        problem "#{formula} is versioned but no #{unversioned_name} formula exists"
-      end
-    elsif ARGV.build_stable? && formula.stable? &&
-          !(versioned_formulae = Dir[formula.path.to_s.gsub(/\.rb$/, "@*.rb")]).empty?
-      versioned_aliases = formula.aliases.grep(/.@\d/)
-      _, last_alias_version =
-        File.basename(versioned_formulae.sort.reverse.first)
-            .gsub(/\.rb$/, "").split("@")
-      major, minor, = formula.version.to_s.split(".")
-      alias_name_major = "#{formula.name}@#{major}"
-      alias_name_major_minor = "#{alias_name_major}.#{minor}"
-      alias_name = if last_alias_version.split(".").length == 1
-        alias_name_major
-      else
-        alias_name_major_minor
-      end
-      valid_alias_names = [alias_name_major, alias_name_major_minor]
+        unless unversioned_formula.exist?
+          unversioned_name = unversioned_formula.basename(".rb")
+          problem "#{formula} is versioned but no #{unversioned_name} formula exists"
+        end
+      elsif ARGV.build_stable? && formula.stable? &&
+            !(versioned_formulae = Dir[formula.path.to_s.gsub(/\.rb$/, "@*.rb")]).empty?
+        versioned_aliases = formula.aliases.grep(/.@\d/)
+        _, last_alias_version =
+          File.basename(versioned_formulae.sort.reverse.first)
+              .gsub(/\.rb$/, "").split("@")
+        major, minor, = formula.version.to_s.split(".")
+        alias_name_major = "#{formula.name}@#{major}"
+        alias_name_major_minor = "#{alias_name_major}.#{minor}"
+        alias_name = if last_alias_version.split(".").length == 1
+          alias_name_major
+        else
+          alias_name_major_minor
+        end
+        valid_alias_names = [alias_name_major, alias_name_major_minor]
 
-      unless formula.tap&.core_tap?
-        versioned_aliases.map! { |a| "#{formula.tap}/#{a}" }
-        valid_alias_names.map! { |a| "#{formula.tap}/#{a}" }
-      end
+        unless formula.tap&.core_tap?
+          versioned_aliases.map! { |a| "#{formula.tap}/#{a}" }
+          valid_alias_names.map! { |a| "#{formula.tap}/#{a}" }
+        end
 
-      valid_versioned_aliases = versioned_aliases & valid_alias_names
-      invalid_versioned_aliases = versioned_aliases - valid_alias_names
+        valid_versioned_aliases = versioned_aliases & valid_alias_names
+        invalid_versioned_aliases = versioned_aliases - valid_alias_names
 
-      if valid_versioned_aliases.empty?
-        if formula.tap
+        if valid_versioned_aliases.empty?
+          if formula.tap
+            problem <<~EOS
+              Formula has other versions so create a versioned alias:
+                cd #{formula.tap.alias_dir}
+                ln -s #{formula.path.to_s.gsub(formula.tap.path, "..")} #{alias_name}
+            EOS
+          else
+            problem "Formula has other versions so create an alias named #{alias_name}."
+          end
+        end
+
+        unless invalid_versioned_aliases.empty?
           problem <<~EOS
-            Formula has other versions so create a versioned alias:
-              cd #{formula.tap.alias_dir}
-              ln -s #{formula.path.to_s.gsub(formula.tap.path, "..")} #{alias_name}
+            Formula has invalid versioned aliases:
+              #{invalid_versioned_aliases.join("\n  ")}
           EOS
-        else
-          problem "Formula has other versions so create an alias named #{alias_name}."
         end
       end
+    end
 
-      unless invalid_versioned_aliases.empty?
-        problem <<~EOS
-          Formula has invalid versioned aliases:
-            #{invalid_versioned_aliases.join("\n  ")}
-        EOS
+    def self.aliases
+      # core aliases + tap alias names + tap alias full name
+      @aliases ||= Formula.aliases + Formula.tap_aliases
+    end
+
+    def audit_formula_name
+      return unless @strict
+      # skip for non-official taps
+      return unless @official_tap
+
+      name = formula.name
+
+      if MissingFormula.blacklisted_reason(name)
+        problem "'#{name}' is blacklisted."
       end
-    end
-  end
 
-  def self.aliases
-    # core aliases + tap alias names + tap alias full name
-    @aliases ||= Formula.aliases + Formula.tap_aliases
-  end
+      if Formula.aliases.include? name
+        problem "Formula name conflicts with existing aliases."
+        return
+      end
 
-  def audit_formula_name
-    return unless @strict
-    # skip for non-official taps
-    return unless @official_tap
+      if oldname = CoreTap.instance.formula_renames[name]
+        problem "'#{name}' is reserved as the old name of #{oldname}"
+        return
+      end
 
-    name = formula.name
+      return if formula.core_formula?
+      return unless Formula.core_names.include?(name)
 
-    if Homebrew::MissingFormula.blacklisted_reason(name)
-      problem "'#{name}' is blacklisted."
+      problem "Formula name conflicts with existing core formula."
     end
 
-    if Formula.aliases.include? name
-      problem "Formula name conflicts with existing aliases."
-      return
-    end
-
-    if oldname = CoreTap.instance.formula_renames[name]
-      problem "'#{name}' is reserved as the old name of #{oldname}"
-      return
-    end
-
-    return if formula.core_formula?
-    return unless Formula.core_names.include?(name)
-
-    problem "Formula name conflicts with existing core formula."
-  end
-
-  def audit_deps
-    @specs.each do |spec|
-      # Check for things we don't like to depend on.
-      # We allow non-Homebrew installs whenever possible.
-      spec.deps.each do |dep|
-        begin
-          dep_f = dep.to_formula
-        rescue TapFormulaUnavailableError
-          # Don't complain about missing cross-tap dependencies
-          next
-        rescue FormulaUnavailableError
-          problem "Can't find dependency #{dep.name.inspect}."
-          next
-        rescue TapFormulaAmbiguityError
-          problem "Ambiguous dependency #{dep.name.inspect}."
-          next
-        rescue TapFormulaWithOldnameAmbiguityError
-          problem "Ambiguous oldname dependency #{dep.name.inspect}."
-          next
-        end
-
-        if dep_f.oldname && dep.name.split("/").last == dep_f.oldname
-          problem "Dependency '#{dep.name}' was renamed; use new name '#{dep_f.name}'."
-        end
-
-        if self.class.aliases.include?(dep.name) &&
-           (dep_f.core_formula? || !dep_f.versioned_formula?)
-          problem "Dependency '#{dep.name}' is an alias; use the canonical name '#{dep.to_formula.full_name}'."
-        end
-
-        if @new_formula && dep_f.keg_only_reason &&
-           !["openssl", "apr", "apr-util"].include?(dep.name) &&
-           [:provided_by_macos, :provided_by_osx].include?(dep_f.keg_only_reason.reason)
-          problem "Dependency '#{dep.name}' may be unnecessary as it is provided by macOS; try to build this formula without it."
-        end
-
-        dep.options.each do |opt|
-          next if dep_f.option_defined?(opt)
-          next if dep_f.requirements.detect do |r|
-            if r.recommended?
-              opt.name == "with-#{r.name}"
-            elsif r.optional?
-              opt.name == "without-#{r.name}"
-            end
+    def audit_deps
+      @specs.each do |spec|
+        # Check for things we don't like to depend on.
+        # We allow non-Homebrew installs whenever possible.
+        spec.deps.each do |dep|
+          begin
+            dep_f = dep.to_formula
+          rescue TapFormulaUnavailableError
+            # Don't complain about missing cross-tap dependencies
+            next
+          rescue FormulaUnavailableError
+            problem "Can't find dependency #{dep.name.inspect}."
+            next
+          rescue TapFormulaAmbiguityError
+            problem "Ambiguous dependency #{dep.name.inspect}."
+            next
+          rescue TapFormulaWithOldnameAmbiguityError
+            problem "Ambiguous oldname dependency #{dep.name.inspect}."
+            next
           end
 
-          problem "Dependency #{dep} does not define option #{opt.name.inspect}"
-        end
+          if dep_f.oldname && dep.name.split("/").last == dep_f.oldname
+            problem "Dependency '#{dep.name}' was renamed; use new name '#{dep_f.name}'."
+          end
 
-        if dep.name == "git"
-          problem "Don't use git as a dependency (it's always available)"
-        end
+          if self.class.aliases.include?(dep.name) &&
+             (dep_f.core_formula? || !dep_f.versioned_formula?)
+            problem "Dependency '#{dep.name}' is an alias; use the canonical name '#{dep.to_formula.full_name}'."
+          end
 
-        if dep.tags.include?(:run)
-          problem "Dependency '#{dep.name}' is marked as :run. Remove :run; it is a no-op."
+          if @new_formula && dep_f.keg_only_reason &&
+             !["openssl", "apr", "apr-util"].include?(dep.name) &&
+             [:provided_by_macos, :provided_by_osx].include?(dep_f.keg_only_reason.reason)
+            problem "Dependency '#{dep.name}' may be unnecessary as it is provided by macOS; try to build this formula without it."
+          end
+
+          dep.options.each do |opt|
+            next if dep_f.option_defined?(opt)
+            next if dep_f.requirements.detect do |r|
+              if r.recommended?
+                opt.name == "with-#{r.name}"
+              elsif r.optional?
+                opt.name == "without-#{r.name}"
+              end
+            end
+
+            problem "Dependency #{dep} does not define option #{opt.name.inspect}"
+          end
+
+          if dep.name == "git"
+            problem "Don't use git as a dependency (it's always available)"
+          end
+
+          if dep.tags.include?(:run)
+            problem "Dependency '#{dep.name}' is marked as :run. Remove :run; it is a no-op."
+          end
         end
       end
     end
-  end
 
-  def audit_conflicts
-    formula.conflicts.each do |c|
+    def audit_conflicts
+      formula.conflicts.each do |c|
+        begin
+          Formulary.factory(c.name)
+        rescue TapFormulaUnavailableError
+          # Don't complain about missing cross-tap conflicts.
+          next
+        rescue FormulaUnavailableError
+          problem "Can't find conflicting formula #{c.name.inspect}."
+        rescue TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError
+          problem "Ambiguous conflicting formula #{c.name.inspect}."
+        end
+      end
+    end
+
+    def audit_keg_only_style
+      return unless @strict
+      return unless formula.keg_only?
+
+      whitelist = %w[
+        Apple
+        macOS
+        OS
+        Homebrew
+        Xcode
+        GPG
+        GNOME
+        BSD
+        Firefox
+      ].freeze
+
+      reason = formula.keg_only_reason.to_s
+      # Formulae names can legitimately be uppercase/lowercase/both.
+      name = Regexp.new(formula.name, Regexp::IGNORECASE)
+      reason.sub!(name, "")
+      first_word = reason.split[0]
+
+      if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
+        problem <<~EOS
+          '#{first_word}' from the keg_only reason should be '#{first_word.downcase}'.
+        EOS
+      end
+
+      return unless reason.end_with?(".")
+      problem "keg_only reason should not end with a period."
+    end
+
+    def audit_homepage
+      homepage = formula.homepage
+
+      return if homepage.nil? || homepage.empty?
+
+      return unless @online
+
+      return unless DevelopmentTools.curl_handles_most_https_certificates?
+      if http_content_problem = curl_check_http_content(homepage,
+                                  user_agents: [:browser, :default],
+                                  check_content: true,
+                                  strict: @strict)
+        problem http_content_problem
+      end
+    end
+
+    def audit_bottle_spec
+      return unless formula.bottle_disabled?
+      return if formula.bottle_disable_reason.valid?
+      problem "Unrecognized bottle modifier"
+    end
+
+    def audit_github_repository
+      return unless @online
+      return unless @new_formula
+
+      regex = %r{https?://github\.com/([^/]+)/([^/]+)/?.*}
+      _, user, repo = *regex.match(formula.stable.url) if formula.stable
+      _, user, repo = *regex.match(formula.homepage) unless user
+      return if !user || !repo
+
+      repo.gsub!(/.git$/, "")
+
       begin
-        Formulary.factory(c.name)
-      rescue TapFormulaUnavailableError
-        # Don't complain about missing cross-tap conflicts.
-        next
-      rescue FormulaUnavailableError
-        problem "Can't find conflicting formula #{c.name.inspect}."
-      rescue TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError
-        problem "Ambiguous conflicting formula #{c.name.inspect}."
+        metadata = GitHub.repository(user, repo)
+      rescue GitHub::HTTPNotFoundError
+        return
+      end
+
+      return if metadata.nil?
+
+      problem "GitHub fork (not canonical repository)" if metadata["fork"]
+      if formula&.tap&.core_tap? &&
+         (metadata["forks_count"] < 20) && (metadata["subscribers_count"] < 20) &&
+         (metadata["stargazers_count"] < 50)
+        problem "GitHub repository not notable enough (<20 forks, <20 watchers and <50 stars)"
+      end
+
+      return if Date.parse(metadata["created_at"]) <= (Date.today - 30)
+      problem "GitHub repository too new (<30 days old)"
+    end
+
+    def audit_specs
+      if head_only?(formula) && formula.tap.to_s.downcase !~ %r{[-/]head-only$}
+        problem "Head-only (no stable download)"
+      end
+
+      if devel_only?(formula) && formula.tap.to_s.downcase !~ %r{[-/]devel-only$}
+        problem "Devel-only (no stable download)"
+      end
+
+      %w[Stable Devel HEAD].each do |name|
+        spec_name = name.downcase.to_sym
+        next unless spec = formula.send(spec_name)
+
+        ra = ResourceAuditor.new(spec, spec_name, online: @online, strict: @strict).audit
+        problems.concat ra.problems.map { |problem| "#{name}: #{problem}" }
+
+        spec.resources.each_value do |resource|
+          ra = ResourceAuditor.new(resource, spec_name, online: @online, strict: @strict).audit
+          problems.concat ra.problems.map { |problem|
+            "#{name} resource #{resource.name.inspect}: #{problem}"
+          }
+        end
+
+        next if spec.patches.empty?
+        next unless @new_formula
+        problem "New formulae should not require patches to build. Patches should be submitted and accepted upstream first."
+      end
+
+      %w[Stable Devel].each do |name|
+        next unless spec = formula.send(name.downcase)
+        version = spec.version
+        if version.to_s !~ /\d/
+          problem "#{name}: version (#{version}) is set to a string without a digit"
+        end
+        if version.to_s.start_with?("HEAD")
+          problem "#{name}: non-HEAD version name (#{version}) should not begin with HEAD"
+        end
+      end
+
+      if formula.stable && formula.devel
+        if formula.devel.version < formula.stable.version
+          problem "devel version #{formula.devel.version} is older than stable version #{formula.stable.version}"
+        elsif formula.devel.version == formula.stable.version
+          problem "stable and devel versions are identical"
+        end
+      end
+
+      if @new_formula && formula.head
+        problem "New formulae should not have a HEAD spec"
+      end
+
+      unstable_whitelist = %w[
+        aalib 1.4rc5
+        angolmois 2.0.0alpha2
+        automysqlbackup 3.0-rc6
+        aview 1.3.0rc1
+        distcc 3.2rc1
+        elm-format 0.6.0-alpha
+        ftgl 2.1.3-rc5
+        hidapi 0.8.0-rc1
+        libcaca 0.99b19
+        nethack4 4.3.0-beta2
+        opensyobon 1.0rc2
+        premake 4.4-beta5
+        pwnat 0.3-beta
+        pxz 4.999.9
+        recode 3.7-beta2
+        speexdsp 1.2rc3
+        sqoop 1.4.6
+        tcptraceroute 1.5beta7
+        testssl 2.8rc3
+        tiny-fugue 5.0b8
+        vbindiff 3.0_beta4
+      ].each_slice(2).to_a.map do |formula, version|
+        [formula, version.sub(/\d+$/, "")]
+      end
+
+      gnome_devel_whitelist = %w[
+        gtk-doc 1.25
+        libart 2.3.21
+        pygtkglext 1.1.0
+        libepoxy 1.5.0
+      ].each_slice(2).to_a.map do |formula, version|
+        [formula, version.split(".")[0..1].join(".")]
+      end
+
+      stable = formula.stable
+      case stable&.url
+      when /[\d\._-](alpha|beta|rc\d)/
+        matched = Regexp.last_match(1)
+        version_prefix = stable.version.to_s.sub(/\d+$/, "")
+        return if unstable_whitelist.include?([formula.name, version_prefix])
+        problem "Stable version URLs should not contain #{matched}"
+      when %r{download\.gnome\.org/sources}, %r{ftp\.gnome\.org/pub/GNOME/sources}i
+        version_prefix = stable.version.to_s.split(".")[0..1].join(".")
+        return if gnome_devel_whitelist.include?([formula.name, version_prefix])
+        version = Version.parse(stable.url)
+        if version >= Version.create("1.0")
+          minor_version = version.to_s.split(".", 3)[1].to_i
+          if minor_version.odd?
+            problem "#{stable.version} is a development release"
+          end
+        end
       end
     end
-  end
 
-  def audit_keg_only_style
-    return unless @strict
-    return unless formula.keg_only?
+    def audit_revision_and_version_scheme
+      return unless formula.tap # skip formula not from core or any taps
+      return unless formula.tap.git? # git log is required
+      return if @new_formula
 
-    whitelist = %w[
-      Apple
-      macOS
-      OS
-      Homebrew
-      Xcode
-      GPG
-      GNOME
-      BSD
-      Firefox
-    ].freeze
+      fv = FormulaVersions.new(formula)
 
-    reason = formula.keg_only_reason.to_s
-    # Formulae names can legitimately be uppercase/lowercase/both.
-    name = Regexp.new(formula.name, Regexp::IGNORECASE)
-    reason.sub!(name, "")
-    first_word = reason.split[0]
+      previous_version_and_checksum = fv.previous_version_and_checksum("origin/master")
+      [:stable, :devel].each do |spec_sym|
+        next unless spec = formula.send(spec_sym)
+        next unless previous_version_and_checksum[spec_sym][:version] == spec.version
+        next if previous_version_and_checksum[spec_sym][:checksum] == spec.checksum
+        problem "#{spec_sym}: sha256 changed without the version also changing; please create an issue upstream to rule out malicious circumstances and to find out why the file changed."
+      end
+
+      attributes = [:revision, :version_scheme]
+      attributes_map = fv.version_attributes_map(attributes, "origin/master")
+
+      current_version_scheme = formula.version_scheme
+      [:stable, :devel].each do |spec|
+        spec_version_scheme_map = attributes_map[:version_scheme][spec]
+        next if spec_version_scheme_map.empty?
+
+        version_schemes = spec_version_scheme_map.values.flatten
+        max_version_scheme = version_schemes.max
+        max_version = spec_version_scheme_map.select do |_, version_scheme|
+          version_scheme.first == max_version_scheme
+        end.keys.max
+
+        if max_version_scheme && current_version_scheme < max_version_scheme
+          problem "version_scheme should not decrease (from #{max_version_scheme} to #{current_version_scheme})"
+        end
+
+        if max_version_scheme && current_version_scheme >= max_version_scheme &&
+           current_version_scheme > 1 &&
+           !version_schemes.include?(current_version_scheme - 1)
+          problem "version_schemes should only increment by 1"
+        end
+
+        formula_spec = formula.send(spec)
+        next unless formula_spec
+
+        spec_version = formula_spec.version
+        next unless max_version
+        next if spec_version >= max_version
+
+        above_max_version_scheme = current_version_scheme > max_version_scheme
+        map_includes_version = spec_version_scheme_map.keys.include?(spec_version)
+        next if !current_version_scheme.zero? &&
+                (above_max_version_scheme || map_includes_version)
+        problem "#{spec} version should not decrease (from #{max_version} to #{spec_version})"
+      end
+
+      current_revision = formula.revision
+      revision_map = attributes_map[:revision][:stable]
+      if formula.stable && !revision_map.empty?
+        stable_revisions = revision_map[formula.stable.version]
+        stable_revisions ||= []
+        max_revision = stable_revisions.max || 0
+
+        if current_revision < max_revision
+          problem "revision should not decrease (from #{max_revision} to #{current_revision})"
+        end
+
+        stable_revisions -= [formula.revision]
+        if !current_revision.zero? && stable_revisions.empty? &&
+           revision_map.keys.length > 1
+          problem "'revision #{formula.revision}' should be removed"
+        elsif current_revision > 1 &&
+              current_revision != max_revision &&
+              !stable_revisions.include?(current_revision - 1)
+          problem "revisions should only increment by 1"
+        end
+      elsif !current_revision.zero? # head/devel-only formula
+        problem "'revision #{current_revision}' should be removed"
+      end
+    end
+
+    def audit_text
+      bin_names = Set.new
+      bin_names << formula.name
+      bin_names += formula.aliases
+      [formula.bin, formula.sbin].each do |dir|
+        next unless dir.exist?
+        bin_names += dir.children.map(&:basename).map(&:to_s)
+      end
+      bin_names.each do |name|
+        ["system", "shell_output", "pipe_output"].each do |cmd|
+          if text =~ %r{(def test|test do).*(#{Regexp.escape(HOMEBREW_PREFIX)}/bin/)?#{cmd}[\(\s]+['"]#{Regexp.escape(name)}[\s'"]}m
+            problem %Q(fully scope test #{cmd} calls e.g. #{cmd} "\#{bin}/#{name}")
+          end
+        end
+      end
+    end
+
+    def audit_lines
+      text.without_patch.split("\n").each_with_index do |line, lineno|
+        line_problems(line, lineno + 1)
+      end
+    end
+
+    def line_problems(line, _lineno)
+      # Check for string interpolation of single values.
+      if line =~ /(system|inreplace|gsub!|change_make_var!).*[ ,]"#\{([\w.]+)\}"/
+        problem "Don't need to interpolate \"#{Regexp.last_match(2)}\" with #{Regexp.last_match(1)}"
+      end
+
+      # Check for string concatenation; prefer interpolation
+      if line =~ /(#\{\w+\s*\+\s*['"][^}]+\})/
+        problem "Try not to concatenate paths in string interpolation:\n   #{Regexp.last_match(1)}"
+      end
+
+      # Prefer formula path shortcuts in Pathname+
+      if line =~ %r{\(\s*(prefix\s*\+\s*(['"])(bin|include|libexec|lib|sbin|share|Frameworks)[/'"])}
+        problem "\"(#{Regexp.last_match(1)}...#{Regexp.last_match(2)})\" should be \"(#{Regexp.last_match(3).downcase}+...)\""
+      end
+
+      problem "Use separate make calls" if line.include?("make && make")
+
+      if line =~ /JAVA_HOME/i && !formula.requirements.map(&:class).include?(JavaRequirement)
+        problem "Use `depends_on :java` to set JAVA_HOME"
+      end
+
+      return unless @strict
+
+      if @official_tap && line.include?("env :std")
+        problem "`env :std` in official tap formulae is deprecated"
+      end
+
+      if line.include?("env :userpaths")
+        problem "`env :userpaths` in formulae is deprecated"
+      end
+
+      if line =~ /system ((["'])[^"' ]*(?:\s[^"' ]*)+\2)/
+        bad_system = Regexp.last_match(1)
+        unless %w[| < > & ; *].any? { |c| bad_system.include? c }
+          good_system = bad_system.gsub(" ", "\", \"")
+          problem "Use `system #{good_system}` instead of `system #{bad_system}` "
+        end
+      end
+
+      problem "`#{Regexp.last_match(1)}` is now unnecessary" if line =~ /(require ["']formula["'])/
+
+      if line =~ %r{#\{share\}/#{Regexp.escape(formula.name)}[/'"]}
+        problem "Use \#{pkgshare} instead of \#{share}/#{formula.name}"
+      end
+
+      if line =~ /depends_on .+ if build\.with(out)?\?\(?["']\w+["']\)?/
+        problem "`Use :optional` or `:recommended` instead of `#{Regexp.last_match(0)}`"
+      end
+
+      return unless line =~ %r{share(\s*[/+]\s*)(['"])#{Regexp.escape(formula.name)}(?:\2|/)}
+      problem "Use pkgshare instead of (share#{Regexp.last_match(1)}\"#{formula.name}\")"
+    end
+
+    def audit_reverse_migration
+      # Only enforce for new formula being re-added to core and official taps
+      return unless @strict
+      return unless @official_tap
+      return unless formula.tap.tap_migrations.key?(formula.name)
 
-    if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
       problem <<~EOS
-        '#{first_word}' from the keg_only reason should be '#{first_word.downcase}'.
+        #{formula.name} seems to be listed in tap_migrations.json!
+        Please remove #{formula.name} from present tap & tap_migrations.json
+        before submitting it to Homebrew/homebrew-#{formula.tap.repo}.
       EOS
     end
 
-    return unless reason.end_with?(".")
-    problem "keg_only reason should not end with a period."
-  end
+    def audit_prefix_has_contents
+      return unless formula.prefix.directory?
+      return unless Keg.new(formula.prefix).empty_installation?
 
-  def audit_homepage
-    homepage = formula.homepage
-
-    return if homepage.nil? || homepage.empty?
-
-    return unless @online
-
-    return unless DevelopmentTools.curl_handles_most_https_certificates?
-    if http_content_problem = curl_check_http_content(homepage,
-                                user_agents: [:browser, :default],
-                                check_content: true,
-                                strict: @strict)
-      problem http_content_problem
-    end
-  end
-
-  def audit_bottle_spec
-    return unless formula.bottle_disabled?
-    return if formula.bottle_disable_reason.valid?
-    problem "Unrecognized bottle modifier"
-  end
-
-  def audit_github_repository
-    return unless @online
-    return unless @new_formula
-
-    regex = %r{https?://github\.com/([^/]+)/([^/]+)/?.*}
-    _, user, repo = *regex.match(formula.stable.url) if formula.stable
-    _, user, repo = *regex.match(formula.homepage) unless user
-    return if !user || !repo
-
-    repo.gsub!(/.git$/, "")
-
-    begin
-      metadata = GitHub.repository(user, repo)
-    rescue GitHub::HTTPNotFoundError
-      return
+      problem <<~EOS
+        The installation seems to be empty. Please ensure the prefix
+        is set correctly and expected files are installed.
+        The prefix configure/make argument may be case-sensitive.
+      EOS
     end
 
-    return if metadata.nil?
+    def audit_url_is_not_binary
+      return unless @official_tap
 
-    problem "GitHub fork (not canonical repository)" if metadata["fork"]
-    if formula&.tap&.core_tap? &&
-       (metadata["forks_count"] < 20) && (metadata["subscribers_count"] < 20) &&
-       (metadata["stargazers_count"] < 50)
-      problem "GitHub repository not notable enough (<20 forks, <20 watchers and <50 stars)"
-    end
+      urls = @specs.map(&:url)
 
-    return if Date.parse(metadata["created_at"]) <= (Date.today - 30)
-    problem "GitHub repository too new (<30 days old)"
-  end
-
-  def audit_specs
-    if head_only?(formula) && formula.tap.to_s.downcase !~ %r{[-/]head-only$}
-      problem "Head-only (no stable download)"
-    end
-
-    if devel_only?(formula) && formula.tap.to_s.downcase !~ %r{[-/]devel-only$}
-      problem "Devel-only (no stable download)"
-    end
-
-    %w[Stable Devel HEAD].each do |name|
-      spec_name = name.downcase.to_sym
-      next unless spec = formula.send(spec_name)
-
-      ra = ResourceAuditor.new(spec, spec_name, online: @online, strict: @strict).audit
-      problems.concat ra.problems.map { |problem| "#{name}: #{problem}" }
-
-      spec.resources.each_value do |resource|
-        ra = ResourceAuditor.new(resource, spec_name, online: @online, strict: @strict).audit
-        problems.concat ra.problems.map { |problem|
-          "#{name} resource #{resource.name.inspect}: #{problem}"
-        }
-      end
-
-      next if spec.patches.empty?
-      next unless @new_formula
-      problem "New formulae should not require patches to build. Patches should be submitted and accepted upstream first."
-    end
-
-    %w[Stable Devel].each do |name|
-      next unless spec = formula.send(name.downcase)
-      version = spec.version
-      if version.to_s !~ /\d/
-        problem "#{name}: version (#{version}) is set to a string without a digit"
-      end
-      if version.to_s.start_with?("HEAD")
-        problem "#{name}: non-HEAD version name (#{version}) should not begin with HEAD"
-      end
-    end
-
-    if formula.stable && formula.devel
-      if formula.devel.version < formula.stable.version
-        problem "devel version #{formula.devel.version} is older than stable version #{formula.stable.version}"
-      elsif formula.devel.version == formula.stable.version
-        problem "stable and devel versions are identical"
-      end
-    end
-
-    unstable_whitelist = %w[
-      aalib 1.4rc5
-      angolmois 2.0.0alpha2
-      automysqlbackup 3.0-rc6
-      aview 1.3.0rc1
-      distcc 3.2rc1
-      elm-format 0.6.0-alpha
-      ftgl 2.1.3-rc5
-      hidapi 0.8.0-rc1
-      libcaca 0.99b19
-      nethack4 4.3.0-beta2
-      opensyobon 1.0rc2
-      premake 4.4-beta5
-      pwnat 0.3-beta
-      pxz 4.999.9
-      recode 3.7-beta2
-      speexdsp 1.2rc3
-      sqoop 1.4.6
-      tcptraceroute 1.5beta7
-      testssl 2.8rc3
-      tiny-fugue 5.0b8
-      vbindiff 3.0_beta4
-    ].each_slice(2).to_a.map do |formula, version|
-      [formula, version.sub(/\d+$/, "")]
-    end
-
-    gnome_devel_whitelist = %w[
-      gtk-doc 1.25
-      libart 2.3.21
-      pygtkglext 1.1.0
-      libepoxy 1.5.0
-    ].each_slice(2).to_a.map do |formula, version|
-      [formula, version.split(".")[0..1].join(".")]
-    end
-
-    stable = formula.stable
-    case stable&.url
-    when /[\d\._-](alpha|beta|rc\d)/
-      matched = Regexp.last_match(1)
-      version_prefix = stable.version.to_s.sub(/\d+$/, "")
-      return if unstable_whitelist.include?([formula.name, version_prefix])
-      problem "Stable version URLs should not contain #{matched}"
-    when %r{download\.gnome\.org/sources}, %r{ftp\.gnome\.org/pub/GNOME/sources}i
-      version_prefix = stable.version.to_s.split(".")[0..1].join(".")
-      return if gnome_devel_whitelist.include?([formula.name, version_prefix])
-      version = Version.parse(stable.url)
-      if version >= Version.create("1.0")
-        minor_version = version.to_s.split(".", 3)[1].to_i
-        if minor_version.odd?
-          problem "#{stable.version} is a development release"
+      urls.each do |url|
+        if url =~ /darwin/i && (url =~ /x86_64/i || url =~ /amd64/i)
+          problem "#{url} looks like a binary package, not a source archive. Official taps are source-only."
         end
       end
     end
-  end
 
-  def audit_revision_and_version_scheme
-    return unless formula.tap # skip formula not from core or any taps
-    return unless formula.tap.git? # git log is required
-    return if @new_formula
-
-    fv = FormulaVersions.new(formula)
-
-    previous_version_and_checksum = fv.previous_version_and_checksum("origin/master")
-    [:stable, :devel].each do |spec_sym|
-      next unless spec = formula.send(spec_sym)
-      next unless previous_version_and_checksum[spec_sym][:version] == spec.version
-      next if previous_version_and_checksum[spec_sym][:checksum] == spec.checksum
-      problem "#{spec_sym}: sha256 changed without the version also changing; please create an issue upstream to rule out malicious circumstances and to find out why the file changed."
+    def quote_dep(dep)
+      dep.is_a?(Symbol) ? dep.inspect : "'#{dep}'"
     end
 
-    attributes = [:revision, :version_scheme]
-    attributes_map = fv.version_attributes_map(attributes, "origin/master")
-
-    current_version_scheme = formula.version_scheme
-    [:stable, :devel].each do |spec|
-      spec_version_scheme_map = attributes_map[:version_scheme][spec]
-      next if spec_version_scheme_map.empty?
-
-      version_schemes = spec_version_scheme_map.values.flatten
-      max_version_scheme = version_schemes.max
-      max_version = spec_version_scheme_map.select do |_, version_scheme|
-        version_scheme.first == max_version_scheme
-      end.keys.max
-
-      if max_version_scheme && current_version_scheme < max_version_scheme
-        problem "version_scheme should not decrease (from #{max_version_scheme} to #{current_version_scheme})"
-      end
-
-      if max_version_scheme && current_version_scheme >= max_version_scheme &&
-         current_version_scheme > 1 &&
-         !version_schemes.include?(current_version_scheme - 1)
-        problem "version_schemes should only increment by 1"
-      end
-
-      formula_spec = formula.send(spec)
-      next unless formula_spec
-
-      spec_version = formula_spec.version
-      next unless max_version
-      next if spec_version >= max_version
-
-      above_max_version_scheme = current_version_scheme > max_version_scheme
-      map_includes_version = spec_version_scheme_map.keys.include?(spec_version)
-      next if !current_version_scheme.zero? &&
-              (above_max_version_scheme || map_includes_version)
-      problem "#{spec} version should not decrease (from #{max_version} to #{spec_version})"
+    def problem_if_output(output)
+      problem(output) if output
     end
 
-    current_revision = formula.revision
-    revision_map = attributes_map[:revision][:stable]
-    if formula.stable && !revision_map.empty?
-      stable_revisions = revision_map[formula.stable.version]
-      stable_revisions ||= []
-      max_revision = stable_revisions.max || 0
-
-      if current_revision < max_revision
-        problem "revision should not decrease (from #{max_revision} to #{current_revision})"
+    def audit
+      only_audits = @only
+      except_audits = @except
+      if only_audits && except_audits
+        odie "--only and --except cannot be used simultaneously!"
       end
 
-      stable_revisions -= [formula.revision]
-      if !current_revision.zero? && stable_revisions.empty? &&
-         revision_map.keys.length > 1
-        problem "'revision #{formula.revision}' should be removed"
-      elsif current_revision > 1 &&
-            current_revision != max_revision &&
-            !stable_revisions.include?(current_revision - 1)
-        problem "revisions should only increment by 1"
+      methods.map(&:to_s).grep(/^audit_/).each do |audit_method_name|
+        name = audit_method_name.gsub(/^audit_/, "")
+        if only_audits
+          next unless only_audits.include?(name)
+        elsif except_audits
+          next if except_audits.include?(name)
+        end
+        send(audit_method_name)
       end
-    elsif !current_revision.zero? # head/devel-only formula
-      problem "'revision #{current_revision}' should be removed"
+    end
+
+    private
+
+    def problem(p)
+      @problems << p
+    end
+
+    def head_only?(formula)
+      formula.head && formula.devel.nil? && formula.stable.nil?
+    end
+
+    def devel_only?(formula)
+      formula.devel && formula.stable.nil?
     end
   end
 
-  def audit_text
-    bin_names = Set.new
-    bin_names << formula.name
-    bin_names += formula.aliases
-    [formula.bin, formula.sbin].each do |dir|
-      next unless dir.exist?
-      bin_names += dir.children.map(&:basename).map(&:to_s)
+  class ResourceAuditor
+    attr_reader :name, :version, :checksum, :url, :mirrors, :using, :specs, :owner
+    attr_reader :spec_name, :problems
+
+    def initialize(resource, spec_name, options = {})
+      @name     = resource.name
+      @version  = resource.version
+      @checksum = resource.checksum
+      @url      = resource.url
+      @mirrors  = resource.mirrors
+      @using    = resource.using
+      @specs    = resource.specs
+      @owner    = resource.owner
+      @spec_name = spec_name
+      @online    = options[:online]
+      @strict    = options[:strict]
+      @problems  = []
     end
-    bin_names.each do |name|
-      ["system", "shell_output", "pipe_output"].each do |cmd|
-        if text =~ %r{(def test|test do).*(#{Regexp.escape(HOMEBREW_PREFIX)}/bin/)?#{cmd}[\(\s]+['"]#{Regexp.escape(name)}[\s'"]}m
-          problem %Q(fully scope test #{cmd} calls e.g. #{cmd} "\#{bin}/#{name}")
+
+    def audit
+      audit_version
+      audit_download_strategy
+      audit_urls
+      self
+    end
+
+    def audit_version
+      if version.nil?
+        problem "missing version"
+      elsif version.to_s.empty?
+        problem "version is set to an empty string"
+      elsif !version.detected_from_url?
+        version_text = version
+        version_url = Version.detect(url, specs)
+        if version_url.to_s == version_text.to_s && version.instance_of?(Version)
+          problem "version #{version_text} is redundant with version scanned from URL"
+        end
+      end
+
+      if version.to_s.start_with?("v")
+        problem "version #{version} should not have a leading 'v'"
+      end
+
+      return unless version.to_s =~ /_\d+$/
+      problem "version #{version} should not end with an underline and a number"
+    end
+
+    def audit_download_strategy
+      if url =~ %r{^(cvs|bzr|hg|fossil)://} || url =~ %r{^(svn)\+http://}
+        problem "Use of the #{$&} scheme is deprecated, pass `:using => :#{Regexp.last_match(1)}` instead"
+      end
+
+      url_strategy = DownloadStrategyDetector.detect(url)
+
+      if using == :git || url_strategy == GitDownloadStrategy
+        if specs[:tag] && !specs[:revision]
+          problem "Git should specify :revision when a :tag is specified."
+        end
+      end
+
+      return unless using
+
+      if using == :ssl3 || \
+         (Object.const_defined?("CurlSSL3DownloadStrategy") && using == CurlSSL3DownloadStrategy)
+        problem "The SSL3 download strategy is deprecated, please choose a different URL"
+      elsif (Object.const_defined?("CurlUnsafeDownloadStrategy") && using == CurlUnsafeDownloadStrategy) || \
+            (Object.const_defined?("UnsafeSubversionDownloadStrategy") && using == UnsafeSubversionDownloadStrategy)
+        problem "#{using.name} is deprecated, please choose a different URL"
+      end
+
+      if using == :cvs
+        mod = specs[:module]
+
+        problem "Redundant :module value in URL" if mod == name
+
+        if url =~ %r{:[^/]+$}
+          mod = url.split(":").last
+
+          if mod == name
+            problem "Redundant CVS module appended to URL"
+          else
+            problem "Specify CVS module as `:module => \"#{mod}\"` instead of appending it to the URL"
+          end
+        end
+      end
+
+      return unless url_strategy == DownloadStrategyDetector.detect("", using)
+      problem "Redundant :using value in URL"
+    end
+
+    def self.curl_openssl_and_deps
+      @curl_openssl_and_deps ||= begin
+        formulae_names = ["curl", "openssl"]
+        formulae_names += formulae_names.flat_map do |f|
+          Formula[f].recursive_dependencies.map(&:name)
+        end
+        formulae_names.uniq
+      rescue FormulaUnavailableError
+        []
+      end
+    end
+
+    def audit_urls
+      urls = [url] + mirrors
+
+      curl_openssl_or_deps = ResourceAuditor.curl_openssl_and_deps.include?(owner.name)
+
+      if spec_name == :stable && curl_openssl_or_deps
+        problem "should not use xz tarballs" if url.end_with?(".xz")
+
+        unless urls.find { |u| u.start_with?("http://") }
+          problem "should always include at least one HTTP mirror"
+        end
+      end
+
+      return unless @online
+      urls.each do |url|
+        next if !@strict && mirrors.include?(url)
+
+        strategy = DownloadStrategyDetector.detect(url, using)
+        if strategy <= CurlDownloadStrategy && !url.start_with?("file")
+          # A `brew mirror`'ed URL is usually not yet reachable at the time of
+          # pull request.
+          next if url =~ %r{^https://dl.bintray.com/homebrew/mirror/}
+          if http_content_problem = curl_check_http_content(url, require_http: curl_openssl_or_deps)
+            problem http_content_problem
+          end
+        elsif strategy <= GitDownloadStrategy
+          unless Utils.git_remote_exists? url
+            problem "The URL #{url} is not a valid git URL"
+          end
+        elsif strategy <= SubversionDownloadStrategy
+          next unless DevelopmentTools.subversion_handles_most_https_certificates?
+          next unless Utils.svn_available?
+          unless Utils.svn_remote_exists? url
+            problem "The URL #{url} is not a valid svn URL"
+          end
         end
       end
     end
-  end
 
-  def audit_lines
-    text.without_patch.split("\n").each_with_index do |line, lineno|
-      line_problems(line, lineno + 1)
+    def problem(text)
+      @problems << text
     end
   end
-
-  def line_problems(line, _lineno)
-    # Check for string interpolation of single values.
-    if line =~ /(system|inreplace|gsub!|change_make_var!).*[ ,]"#\{([\w.]+)\}"/
-      problem "Don't need to interpolate \"#{Regexp.last_match(2)}\" with #{Regexp.last_match(1)}"
-    end
-
-    # Check for string concatenation; prefer interpolation
-    if line =~ /(#\{\w+\s*\+\s*['"][^}]+\})/
-      problem "Try not to concatenate paths in string interpolation:\n   #{Regexp.last_match(1)}"
-    end
-
-    # Prefer formula path shortcuts in Pathname+
-    if line =~ %r{\(\s*(prefix\s*\+\s*(['"])(bin|include|libexec|lib|sbin|share|Frameworks)[/'"])}
-      problem "\"(#{Regexp.last_match(1)}...#{Regexp.last_match(2)})\" should be \"(#{Regexp.last_match(3).downcase}+...)\""
-    end
-
-    problem "Use separate make calls" if line.include?("make && make")
-
-    if line =~ /JAVA_HOME/i && !formula.requirements.map(&:class).include?(JavaRequirement)
-      problem "Use `depends_on :java` to set JAVA_HOME"
-    end
-
-    return unless @strict
-
-    if @official_tap && line.include?("env :std")
-      problem "`env :std` in official tap formulae is deprecated"
-    end
-
-    if line.include?("env :userpaths")
-      problem "`env :userpaths` in formulae is deprecated"
-    end
-
-    if line =~ /system ((["'])[^"' ]*(?:\s[^"' ]*)+\2)/
-      bad_system = Regexp.last_match(1)
-      unless %w[| < > & ; *].any? { |c| bad_system.include? c }
-        good_system = bad_system.gsub(" ", "\", \"")
-        problem "Use `system #{good_system}` instead of `system #{bad_system}` "
-      end
-    end
-
-    problem "`#{Regexp.last_match(1)}` is now unnecessary" if line =~ /(require ["']formula["'])/
-
-    if line =~ %r{#\{share\}/#{Regexp.escape(formula.name)}[/'"]}
-      problem "Use \#{pkgshare} instead of \#{share}/#{formula.name}"
-    end
-
-    return unless line =~ %r{share(\s*[/+]\s*)(['"])#{Regexp.escape(formula.name)}(?:\2|/)}
-    problem "Use pkgshare instead of (share#{Regexp.last_match(1)}\"#{formula.name}\")"
-  end
-
-  def audit_reverse_migration
-    # Only enforce for new formula being re-added to core and official taps
-    return unless @strict
-    return unless @official_tap
-    return unless formula.tap.tap_migrations.key?(formula.name)
-
-    problem <<~EOS
-      #{formula.name} seems to be listed in tap_migrations.json!
-      Please remove #{formula.name} from present tap & tap_migrations.json
-      before submitting it to Homebrew/homebrew-#{formula.tap.repo}.
-    EOS
-  end
-
-  def audit_prefix_has_contents
-    return unless formula.prefix.directory?
-    return unless Keg.new(formula.prefix).empty_installation?
-
-    problem <<~EOS
-      The installation seems to be empty. Please ensure the prefix
-      is set correctly and expected files are installed.
-      The prefix configure/make argument may be case-sensitive.
-    EOS
-  end
-
-  def audit_url_is_not_binary
-    return unless @official_tap
-
-    urls = @specs.map(&:url)
-
-    urls.each do |url|
-      if url =~ /darwin/i && (url =~ /x86_64/i || url =~ /amd64/i)
-        problem "#{url} looks like a binary package, not a source archive. Official taps are source-only."
-      end
-    end
-  end
-
-  def quote_dep(dep)
-    dep.is_a?(Symbol) ? dep.inspect : "'#{dep}'"
-  end
-
-  def problem_if_output(output)
-    problem(output) if output
-  end
-
-  def audit
-    only_audits = @only
-    except_audits = @except
-    if only_audits && except_audits
-      odie "--only and --except cannot be used simultaneously!"
-    end
-
-    methods.map(&:to_s).grep(/^audit_/).each do |audit_method_name|
-      name = audit_method_name.gsub(/^audit_/, "")
-      if only_audits
-        next unless only_audits.include?(name)
-      elsif except_audits
-        next if except_audits.include?(name)
-      end
-      send(audit_method_name)
-    end
-  end
-
-  private
-
-  def problem(p)
-    @problems << p
-  end
-
-  def head_only?(formula)
-    formula.head && formula.devel.nil? && formula.stable.nil?
-  end
-
-  def devel_only?(formula)
-    formula.devel && formula.stable.nil?
-  end
-end
-
-class ResourceAuditor
-  attr_reader :name, :version, :checksum, :url, :mirrors, :using, :specs, :owner
-  attr_reader :spec_name, :problems
-
-  def initialize(resource, spec_name, options = {})
-    @name     = resource.name
-    @version  = resource.version
-    @checksum = resource.checksum
-    @url      = resource.url
-    @mirrors  = resource.mirrors
-    @using    = resource.using
-    @specs    = resource.specs
-    @owner    = resource.owner
-    @spec_name = spec_name
-    @online    = options[:online]
-    @strict    = options[:strict]
-    @problems  = []
-  end
-
-  def audit
-    audit_version
-    audit_download_strategy
-    audit_urls
-    self
-  end
-
-  def audit_version
-    if version.nil?
-      problem "missing version"
-    elsif version.to_s.empty?
-      problem "version is set to an empty string"
-    elsif !version.detected_from_url?
-      version_text = version
-      version_url = Version.detect(url, specs)
-      if version_url.to_s == version_text.to_s && version.instance_of?(Version)
-        problem "version #{version_text} is redundant with version scanned from URL"
-      end
-    end
-
-    if version.to_s.start_with?("v")
-      problem "version #{version} should not have a leading 'v'"
-    end
-
-    return unless version.to_s =~ /_\d+$/
-    problem "version #{version} should not end with an underline and a number"
-  end
-
-  def audit_download_strategy
-    if url =~ %r{^(cvs|bzr|hg|fossil)://} || url =~ %r{^(svn)\+http://}
-      problem "Use of the #{$&} scheme is deprecated, pass `:using => :#{Regexp.last_match(1)}` instead"
-    end
-
-    url_strategy = DownloadStrategyDetector.detect(url)
-
-    if using == :git || url_strategy == GitDownloadStrategy
-      if specs[:tag] && !specs[:revision]
-        problem "Git should specify :revision when a :tag is specified."
-      end
-    end
-
-    return unless using
-
-    if using == :ssl3 || \
-       (Object.const_defined?("CurlSSL3DownloadStrategy") && using == CurlSSL3DownloadStrategy)
-      problem "The SSL3 download strategy is deprecated, please choose a different URL"
-    elsif (Object.const_defined?("CurlUnsafeDownloadStrategy") && using == CurlUnsafeDownloadStrategy) || \
-          (Object.const_defined?("UnsafeSubversionDownloadStrategy") && using == UnsafeSubversionDownloadStrategy)
-      problem "#{using.name} is deprecated, please choose a different URL"
-    end
-
-    if using == :cvs
-      mod = specs[:module]
-
-      problem "Redundant :module value in URL" if mod == name
-
-      if url =~ %r{:[^/]+$}
-        mod = url.split(":").last
-
-        if mod == name
-          problem "Redundant CVS module appended to URL"
-        else
-          problem "Specify CVS module as `:module => \"#{mod}\"` instead of appending it to the URL"
-        end
-      end
-    end
-
-    return unless url_strategy == DownloadStrategyDetector.detect("", using)
-    problem "Redundant :using value in URL"
-  end
-
-  def self.curl_openssl_and_deps
-    @curl_openssl_and_deps ||= begin
-      formulae_names = ["curl", "openssl"]
-      formulae_names += formulae_names.flat_map do |f|
-        Formula[f].recursive_dependencies.map(&:name)
-      end
-      formulae_names.uniq
-    rescue FormulaUnavailableError
-      []
-    end
-  end
-
-  def audit_urls
-    urls = [url] + mirrors
-
-    curl_openssl_or_deps = ResourceAuditor.curl_openssl_and_deps.include?(owner.name)
-
-    if spec_name == :stable && curl_openssl_or_deps
-      problem "should not use xz tarballs" if url.end_with?(".xz")
-
-      unless urls.find { |u| u.start_with?("http://") }
-        problem "should always include at least one HTTP mirror"
-      end
-    end
-
-    return unless @online
-    urls.each do |url|
-      next if !@strict && mirrors.include?(url)
-
-      strategy = DownloadStrategyDetector.detect(url, using)
-      if strategy <= CurlDownloadStrategy && !url.start_with?("file")
-        # A `brew mirror`'ed URL is usually not yet reachable at the time of
-        # pull request.
-        next if url =~ %r{^https://dl.bintray.com/homebrew/mirror/}
-        if http_content_problem = curl_check_http_content(url, require_http: curl_openssl_or_deps)
-          problem http_content_problem
-        end
-      elsif strategy <= GitDownloadStrategy
-        unless Utils.git_remote_exists? url
-          problem "The URL #{url} is not a valid git URL"
-        end
-      elsif strategy <= SubversionDownloadStrategy
-        next unless DevelopmentTools.subversion_handles_most_https_certificates?
-        next unless Utils.svn_available?
-        unless Utils.svn_remote_exists? url
-          problem "The URL #{url} is not a valid svn URL"
-        end
-      end
-    end
-  end
-
-  def problem(text)
-    @problems << text
-  end
 end
diff --git a/Library/Homebrew/dev-cmd/bottle.rb b/Library/Homebrew/dev-cmd/bottle.rb
index b05277d054..ab222b8832 100644
--- a/Library/Homebrew/dev-cmd/bottle.rb
+++ b/Library/Homebrew/dev-cmd/bottle.rb
@@ -1,4 +1,4 @@
-#:  * `bottle` [`--verbose`] [`--no-rebuild`|`--keep-old`] [`--skip-relocation`] [`--root-url=`<URL>] [`--force-core-tap`] <formulae>:
+#:  * `bottle` [`--verbose`] [`--no-rebuild`|`--keep-old`] [`--skip-relocation`] [`--or-later`] [`--root-url=`<URL>] [`--force-core-tap`] <formulae>:
 #:    Generate a bottle (binary package) from a formula installed with
 #:    `--build-bottle`.
 #:
@@ -15,6 +15,8 @@
 #:    If `--root-url` is passed, use the specified <URL> as the root of the
 #:    bottle's URL instead of Homebrew's default.
 #:
+#:    If `--or-later` is passed, append _or_later to the bottle tag.
+#:
 #:    If `--force-core-tap` is passed, build a bottle even if <formula> is not
 #:    in homebrew/core or any installed taps.
 #:
@@ -37,7 +39,6 @@ require "formula_versions"
 require "cli_parser"
 require "utils/inreplace"
 require "erb"
-require "extend/pathname"
 
 BOTTLE_ERB = <<-EOS.freeze
   bottle do
@@ -58,7 +59,7 @@ BOTTLE_ERB = <<-EOS.freeze
     <% checksums.each do |checksum_type, checksum_values| %>
     <% checksum_values.each do |checksum_value| %>
     <% checksum, macos = checksum_value.shift %>
-    <%= checksum_type %> "<%= checksum %>" => :<%= macos %>
+    <%= checksum_type %> "<%= checksum %>" => :<%= macos %><%= "_or_later" if Homebrew.args.or_later? %>
     <% end %>
     <% end %>
   end
@@ -79,7 +80,9 @@ module Homebrew
       switch "--write"
       switch "--no-commit"
       switch "--json"
+      switch "--or-later"
       switch :verbose
+      switch :debug
       flag   "--root-url"
     end
 
@@ -114,7 +117,7 @@ module Homebrew
       linked_libraries = Keg.file_linked_libraries(file, string)
       result ||= !linked_libraries.empty?
 
-      if @args.verbose?
+      if Homebrew.args.verbose?
         print_filename.call(string, file) unless linked_libraries.empty?
         linked_libraries.each do |lib|
           puts " #{Tty.bold}-->#{Tty.reset} links to #{lib}"
@@ -137,7 +140,7 @@ module Homebrew
         end
       end
 
-      next unless @args.verbose? && !text_matches.empty?
+      next unless Homebrew.args.verbose? && !text_matches.empty?
       print_filename.call(string, file)
       text_matches.first(MAXIMUM_STRING_MATCHES).each do |match, offset|
         puts " #{Tty.bold}-->#{Tty.reset} match '#{match}' at offset #{Tty.bold}0x#{offset}#{Tty.reset}"
@@ -158,7 +161,7 @@ module Homebrew
       absolute_symlinks_start_with_string << pn if link.to_s.start_with?(string)
     end
 
-    if @args.verbose?
+    if Homebrew.args.verbose?
       unless absolute_symlinks_start_with_string.empty?
         opoo "Absolute symlink starting with #{string}:"
         absolute_symlinks_start_with_string.each do |pn|
@@ -299,7 +302,7 @@ module Homebrew
           end
           skip_relocation = relocatable && !keg.require_relocation?
         end
-        puts if !relocatable && @args.verbose?
+        puts if !relocatable && Homebrew.args.verbose?
       rescue Interrupt
         ignore_interrupts { bottle_path.unlink if bottle_path.exist? }
         raise
@@ -360,6 +363,8 @@ module Homebrew
     puts output
 
     return unless @args.json?
+    tag = Utils::Bottles.tag.to_s
+    tag += "_or_later" if @args.or_later?
     json = {
       f.full_name => {
         "formula" => {
@@ -372,7 +377,7 @@ module Homebrew
           "cellar" => bottle.cellar.to_s,
           "rebuild" => bottle.rebuild,
           "tags" => {
-            Utils::Bottles.tag.to_s => {
+            tag => {
               "filename" => filename.to_s,
               "sha256" => sha256,
             },
diff --git a/Library/Homebrew/dev-cmd/bump-formula-pr.rb b/Library/Homebrew/dev-cmd/bump-formula-pr.rb
index 1f44fa549e..b5c1dccdd7 100644
--- a/Library/Homebrew/dev-cmd/bump-formula-pr.rb
+++ b/Library/Homebrew/dev-cmd/bump-formula-pr.rb
@@ -131,6 +131,9 @@ module Homebrew
       ENV[env] = homebrew_env
     end
 
+    gh_api_errors = [GitHub::AuthenticationFailedError, GitHub::HTTPNotFoundError,
+                     GitHub::RateLimitExceededError, GitHub::Error, JSON::ParserError].freeze
+
     formula = ARGV.formulae.first
 
     if formula
@@ -314,73 +317,41 @@ module Homebrew
       end
     end
 
-    unless Formula["hub"].any_version_installed?
-      if ARGV.dry_run?
-        ohai "brew install hub"
-      else
-        safe_system "brew", "install", "hub"
-      end
-    end
-
     formula.path.parent.cd do
       branch = "#{formula.name}-#{new_formula_version}"
       git_dir = Utils.popen_read("git rev-parse --git-dir").chomp
       shallow = !git_dir.empty? && File.exist?("#{git_dir}/shallow")
 
-      hub_args = []
-      git_final_checkout_args = []
-      if ARGV.include?("--no-browse")
-        git_final_checkout_args << "--quiet"
-      else
-        hub_args << "--browse"
-      end
-
       if ARGV.dry_run?
-        ohai "hub fork # read $HUB_REMOTE"
+        ohai "fork repository with GitHub API"
         ohai "git fetch --unshallow origin" if shallow
         ohai "git checkout --no-track -b #{branch} origin/master"
         ohai "git commit --no-edit --verbose --message='#{formula.name} #{new_formula_version}#{devel_message}' -- #{formula.path}"
         ohai "git push --set-upstream $HUB_REMOTE #{branch}:#{branch}"
-        ohai "hub pull-request #{hub_args.join(" ")} -m '#{formula.name} #{new_formula_version}#{devel_message}'"
+        ohai "create pull request with GitHub API"
         ohai "git checkout -"
       else
-        reply = IO.popen(["hub", "fork"], "r+", err: "/dev/null") do |io|
-          reader = Thread.new { io.read }
-          sleep 1
-          io.close_write
-          reader.value
-        end
 
-        if reply.to_s.include? "username:"
+        begin
+          response = GitHub.create_fork(formula.tap.full_name)
+          # GitHub API responds immediately but fork takes a few seconds to be ready.
+          sleep 3
+        rescue *gh_api_errors => e
           formula.path.atomic_write(backup_file) unless ARGV.dry_run?
-          git_path = "$(brew --repo #{formula.tap})" if formula.tap
-          git_path ||= formula.path.parent
-          odie <<~EOS
-            Retry after configuring hub by running:
-              hub -C "#{git_path}" fork
-            Or setting HOMEBREW_GITHUB_TOKEN with at least 'public_repo' scope.
-          EOS
+          odie "Unable to fork: #{e.message}!"
         end
 
-        remote = reply[/remote:? (\S+)/, 1]
-
-        # repeat for hub 2.2 backwards compatibility:
-        remote = Utils.popen_read("hub", "fork", err: :out)[/remote:? (\S+)/, 1] if remote.to_s.empty?
-
-        if remote.to_s.empty?
-          formula.path.atomic_write(backup_file) unless ARGV.dry_run?
-          odie "cannot get remote from 'hub'!"
-        end
+        remote_url = response.fetch("clone_url")
+        username = response.fetch("owner").fetch("login")
 
         safe_system "git", "fetch", "--unshallow", "origin" if shallow
         safe_system "git", "checkout", "--no-track", "-b", branch, "origin/master"
         safe_system "git", "commit", "--no-edit", "--verbose",
           "--message=#{formula.name} #{new_formula_version}#{devel_message}",
           "--", formula.path
-        safe_system "git", "push", "--set-upstream", remote, "#{branch}:#{branch}"
+        safe_system "git", "push", "--set-upstream", remote_url, "#{branch}:#{branch}"
+        safe_system "git", "checkout", "--quiet", "-"
         pr_message = <<~EOS
-          #{formula.name} #{new_formula_version}#{devel_message}
-
           Created with `brew bump-formula-pr`.
         EOS
         user_message = ARGV.value("message")
@@ -391,8 +362,19 @@ module Homebrew
             #{user_message}
           EOS
         end
-        safe_system "hub", "pull-request", *hub_args, "-m", pr_message
-        safe_system "git", "checkout", *git_final_checkout_args, "-"
+        pr_title = "#{formula.name} #{new_formula_version}#{devel_message}"
+
+        begin
+          url = GitHub.create_pull_request(formula.tap.full_name, pr_title,
+                                           "#{username}:#{branch}", "master", pr_message)["html_url"]
+          if ARGV.include?("--no-browse")
+            puts url
+          else
+            exec_browser url
+          end
+        rescue *gh_api_errors => e
+          odie "Unable to open pull request: #{e.message}!"
+        end
       end
     end
   end
diff --git a/Library/Homebrew/dev-cmd/create.rb b/Library/Homebrew/dev-cmd/create.rb
index 514d3b6c30..d9905a39da 100644
--- a/Library/Homebrew/dev-cmd/create.rb
+++ b/Library/Homebrew/dev-cmd/create.rb
@@ -65,7 +65,7 @@ module Homebrew
     # Don't allow blacklisted formula, or names that shadow aliases,
     # unless --force is specified.
     unless ARGV.force?
-      if reason = Homebrew::MissingFormula.blacklisted_reason(fc.name)
+      if reason = MissingFormula.blacklisted_reason(fc.name)
         raise "#{fc.name} is blacklisted for creation.\n#{reason}\nIf you really want to create this formula use --force."
       end
 
@@ -185,8 +185,9 @@ class FormulaCreator
       <% if mode == :cmake %>
         depends_on "cmake" => :build
       <% elsif mode == :meson %>
-        depends_on "meson" => :build
+        depends_on "meson-internal" => :build
         depends_on "ninja" => :build
+        depends_on "python" => :build
       <% elsif mode.nil? %>
         # depends_on "cmake" => :build
       <% end %>
@@ -202,10 +203,11 @@ class FormulaCreator
                                 "--disable-silent-rules",
                                 "--prefix=\#{prefix}"
       <% elsif mode == :meson %>
+          ENV.refurbish_args
+
           mkdir "build" do
             system "meson", "--prefix=\#{prefix}", ".."
             system "ninja"
-            system "ninja", "test"
             system "ninja", "install"
           end
       <% else %>
diff --git a/Library/Homebrew/dev-cmd/edit.rb b/Library/Homebrew/dev-cmd/edit.rb
index 0861a4bb1e..bcbf5b7d5d 100644
--- a/Library/Homebrew/dev-cmd/edit.rb
+++ b/Library/Homebrew/dev-cmd/edit.rb
@@ -11,8 +11,10 @@ module Homebrew
   module_function
 
   def edit
-    args = Homebrew::CLI::Parser.parse do
-      switch "--force"
+    Homebrew::CLI::Parser.parse do
+      switch :force
+      switch :verbose
+      switch :debug
     end
 
     unless (HOMEBREW_REPOSITORY/".git").directory?
@@ -41,7 +43,7 @@ module Homebrew
       paths = ARGV.named.map do |name|
         path = Formulary.path(name)
 
-        raise FormulaUnavailableError, name unless path.file? || args.force?
+        raise FormulaUnavailableError, name unless path.file? || Homebrew.args.force?
 
         path
       end
diff --git a/Library/Homebrew/dev-cmd/formula.rb b/Library/Homebrew/dev-cmd/formula.rb
index 67d11edce2..eb6cd087ea 100644
--- a/Library/Homebrew/dev-cmd/formula.rb
+++ b/Library/Homebrew/dev-cmd/formula.rb
@@ -2,11 +2,17 @@
 #:    Display the path where <formula> is located.
 
 require "formula"
+require "cli_parser"
 
 module Homebrew
   module_function
 
   def formula
+    Homebrew::CLI::Parser.parse do
+      switch :debug
+      switch :verbose
+    end
+
     raise FormulaUnspecifiedError if ARGV.named.empty?
     ARGV.resolved_formulae.each { |f| puts f.path }
   end
diff --git a/Library/Homebrew/dev-cmd/linkage.rb b/Library/Homebrew/dev-cmd/linkage.rb
index c33c181a1e..834ed066ed 100644
--- a/Library/Homebrew/dev-cmd/linkage.rb
+++ b/Library/Homebrew/dev-cmd/linkage.rb
@@ -21,7 +21,7 @@ module Homebrew
       result = LinkageChecker.new(keg)
       if ARGV.include?("--test")
         result.display_test_output
-        Homebrew.failed = true if result.broken_dylibs?
+        Homebrew.failed = true if result.broken_library_linkage?
       elsif ARGV.include?("--reverse")
         result.display_reverse_output
       else
diff --git a/Library/Homebrew/dev-cmd/mirror.rb b/Library/Homebrew/dev-cmd/mirror.rb
index bf19ee3c57..7e3f2821f9 100644
--- a/Library/Homebrew/dev-cmd/mirror.rb
+++ b/Library/Homebrew/dev-cmd/mirror.rb
@@ -1,11 +1,18 @@
 #: @hide_from_man_page
-#:  * `mirror` [`--test`] <formulae>:
+#:  * `mirror` <formulae>:
 #:    Reuploads the stable URL for a formula to Bintray to use it as a mirror.
 
+require "cli_parser"
+
 module Homebrew
   module_function
 
   def mirror
+    Homebrew::CLI::Parser.parse do
+      switch :debug
+      switch :verbose
+    end
+
     odie "This command requires at least formula argument!" if ARGV.named.empty?
 
     bintray_user = ENV["HOMEBREW_BINTRAY_USER"]
diff --git a/Library/Homebrew/dev-cmd/pull.rb b/Library/Homebrew/dev-cmd/pull.rb
index c8006d7781..3947846963 100644
--- a/Library/Homebrew/dev-cmd/pull.rb
+++ b/Library/Homebrew/dev-cmd/pull.rb
@@ -50,12 +50,10 @@
 
 require "net/http"
 require "net/https"
-require "utils"
 require "json"
 require "cli_parser"
 require "formula"
 require "formulary"
-require "tap"
 require "version"
 require "pkg_version"
 
@@ -86,8 +84,10 @@ module Homebrew
       switch "--no-pbcopy"
       switch "--no-publish"
       switch "--warn-on-publish-failure"
-      flag   "--bintray-org",   required: true
-      flag   "--test-bot-user", required: true
+      switch :verbose
+      switch :debug
+      flag   "--bintray-org="
+      flag   "--test-bot-user="
     end
 
     if ARGV.named.empty?
diff --git a/Library/Homebrew/dev-cmd/release-notes.rb b/Library/Homebrew/dev-cmd/release-notes.rb
index 892a4a83e1..a930aad23f 100644
--- a/Library/Homebrew/dev-cmd/release-notes.rb
+++ b/Library/Homebrew/dev-cmd/release-notes.rb
@@ -1,6 +1,6 @@
 #:  * `release-notes` [`--markdown`] [<previous_tag>] [<end_ref>]:
 #:    Output the merged pull requests on Homebrew/brew between two Git refs.
-#:    If no <previous_tag> is provided it defaults to the newest tag.
+#:    If no <previous_tag> is provided it defaults to the latest tag.
 #:    If no <end_ref> is provided it defaults to `origin/master`.
 #:
 #:    If `--markdown` is passed, output as a Markdown list.
@@ -16,19 +16,21 @@ module Homebrew
     end
 
     previous_tag = ARGV.named.first
-    previous_tag ||= Utils.popen_read("git tag --list --sort=-version:refname")
-                          .lines.first.chomp
+    previous_tag ||= Utils.popen_read(
+      "git", "-C", HOMEBREW_REPOSITORY, "tag", "--list", "--sort=-version:refname"
+    ).lines.first.chomp
     odie "Could not find any previous tags!" unless previous_tag
 
     end_ref = ARGV.named[1] || "origin/master"
 
     [previous_tag, end_ref].each do |ref|
-      next if quiet_system "git", "rev-parse", "--verify", "--quiet", ref
+      next if quiet_system "git", "-C", HOMEBREW_REPOSITORY, "rev-parse", "--verify", "--quiet", ref
       odie "Ref #{ref} does not exist!"
     end
 
-    output = Utils.popen_read("git log --pretty=format:'%s >> - %b%n' '#{previous_tag}'..'#{end_ref}'")
-                  .lines.grep(/Merge pull request/)
+    output = Utils.popen_read(
+      "git", "-C", HOMEBREW_REPOSITORY, "log", "--pretty=format:'%s >> - %b%n'", "#{previous_tag}..#{end_ref}"
+    ).lines.grep(/Merge pull request/)
 
     output.map! do |s|
       s.gsub(%r{.*Merge pull request #(\d+) from ([^/]+)/[^>]*(>>)*},
diff --git a/Library/Homebrew/dev-cmd/tap-new.rb b/Library/Homebrew/dev-cmd/tap-new.rb
index 31299d2b0b..e29b143c39 100644
--- a/Library/Homebrew/dev-cmd/tap-new.rb
+++ b/Library/Homebrew/dev-cmd/tap-new.rb
@@ -2,6 +2,7 @@
 #:    Generate the template files for a new tap.
 
 require "tap"
+require "cli_parser"
 
 module Homebrew
   module_function
@@ -14,6 +15,11 @@ module Homebrew
   end
 
   def tap_new
+    Homebrew::CLI::Parser.parse do
+      switch :debug
+      switch :verbose
+    end
+
     raise "A tap argument is required" if ARGV.named.empty?
 
     tap = Tap.fetch(ARGV.named.first)
diff --git a/Library/Homebrew/dev-cmd/tests.rb b/Library/Homebrew/dev-cmd/tests.rb
index 57c00dafc7..3edc12ed5b 100644
--- a/Library/Homebrew/dev-cmd/tests.rb
+++ b/Library/Homebrew/dev-cmd/tests.rb
@@ -17,7 +17,6 @@
 
 require "cli_parser"
 require "fileutils"
-require "tap"
 
 module Homebrew
   module_function
@@ -26,11 +25,12 @@ module Homebrew
     args = Homebrew::CLI::Parser.parse do
       switch "--no-compat"
       switch "--generic"
-      switch "-v", "--verbose"
       switch "--coverage"
       switch "--online"
-      flag   "--only", required: true
-      flag   "--seed", required: true
+      switch :debug
+      switch :verbose
+      flag   "--only="
+      flag   "--seed="
     end
 
     HOMEBREW_LIBRARY_PATH.cd do
@@ -113,6 +113,7 @@ module Homebrew
       end
 
       unless OS.linux?
+        args << "--tag" << "~needs_linux"
         files = files.reject { |p| p =~ %r{^test/os/linux(/.*|_spec\.rb)$} }
       end
 
diff --git a/Library/Homebrew/dev-cmd/update-test.rb b/Library/Homebrew/dev-cmd/update-test.rb
index c0e3f64a00..d72e12b249 100644
--- a/Library/Homebrew/dev-cmd/update-test.rb
+++ b/Library/Homebrew/dev-cmd/update-test.rb
@@ -23,8 +23,10 @@ module Homebrew
     args = Homebrew::CLI::Parser.parse do
       switch "--to-tag"
       switch "--keep-tmp"
-      flag   "--commit", required: true
-      flag   "--before", required: true
+      switch :verbose
+      switch :debug
+      flag   "--commit="
+      flag   "--before="
     end
 
     ENV["HOMEBREW_UPDATE_TEST"] = "1"
diff --git a/Library/Homebrew/diagnostic.rb b/Library/Homebrew/diagnostic.rb
index 36df53794f..736f35ff19 100644
--- a/Library/Homebrew/diagnostic.rb
+++ b/Library/Homebrew/diagnostic.rb
@@ -107,18 +107,6 @@ module Homebrew
         EOS
       end
 
-      # See https://github.com/Homebrew/legacy-homebrew/pull/9986
-      def check_path_for_trailing_slashes
-        bad_paths = PATH.new(ENV["HOMEBREW_PATH"]).select { |p| p.end_with?("/") }
-        return if bad_paths.empty?
-
-        inject_file_list bad_paths, <<~EOS
-          Some directories in your path end in a slash.
-          Directories in your path should not end in a slash. This can break other
-          doctor checks. The following directories should be edited:
-        EOS
-      end
-
       # Anaconda installs multiple system & brew dupes, including OpenSSL, Python,
       # sqlite, libpng, Qt, etc. Regularly breaks compile on Vim, MacVim and others.
       # Is flagged as part of the *-config script checks below, but people seem
@@ -492,21 +480,6 @@ module Homebrew
         EOS
       end
 
-      def check_user_curlrc
-        curlrc_found = %w[CURL_HOME HOME].any? do |var|
-          ENV[var] && File.exist?("#{ENV[var]}/.curlrc")
-        end
-        return unless curlrc_found
-
-        <<~EOS
-          You have a curlrc file
-          If you have trouble downloading packages with Homebrew, then maybe this
-          is the problem? If the following command doesn't work, then try removing
-          your curlrc:
-            curl #{Formatter.url("https://github.com")}
-        EOS
-      end
-
       def check_for_gettext
         find_relative_paths("lib/libgettextlib.dylib",
                             "lib/libintl.dylib",
@@ -620,18 +593,6 @@ module Homebrew
         message
       end
 
-      def check_ssl_cert_file
-        return unless ENV.key?("SSL_CERT_FILE")
-        <<~EOS
-          Setting SSL_CERT_FILE can break downloading files; if that happens
-          you should unset it before running Homebrew.
-
-          Homebrew uses the system curl which uses system certificates by
-          default. Setting SSL_CERT_FILE makes it use an outdated OpenSSL, which
-          does not support modern OpenSSL certificate stores.
-        EOS
-      end
-
       def check_for_symlinked_cellar
         return unless HOMEBREW_CELLAR.exist?
         return unless HOMEBREW_CELLAR.symlink?
@@ -811,28 +772,6 @@ module Homebrew
         false
       end
 
-      def check_for_linked_keg_only_brews
-        return unless HOMEBREW_CELLAR.exist?
-
-        linked = Formula.installed.sort.select do |f|
-          f.keg_only? && __check_linked_brew(f)
-        end
-        return if linked.empty?
-
-        inject_file_list linked.map(&:full_name), <<~EOS
-          Some keg-only formulae are linked into the Cellar.
-          Linking a keg-only formula, such as gettext, into the cellar with
-          `brew link <formula>` will cause other formulae to detect them during
-          the `./configure` step. This may cause problems when compiling those
-          other formulae.
-
-          Binaries provided by keg-only formulae may override system binaries
-          with other strange results.
-
-          You may wish to `brew unlink` these brews:
-        EOS
-      end
-
       def check_for_other_frameworks
         # Other frameworks that are known to cause problems when present
         frameworks_to_check = %w[
@@ -893,53 +832,6 @@ module Homebrew
         EOS
       end
 
-      def check_for_enthought_python
-        return unless which "enpkg"
-
-        <<~EOS
-          Enthought Python was found in your PATH.
-          This can cause build problems, as this software installs its own
-          copies of iconv and libxml2 into directories that are picked up by
-          other build systems.
-        EOS
-      end
-
-      def check_for_library_python
-        return unless File.exist?("/Library/Frameworks/Python.framework")
-
-        <<~EOS
-          Python is installed at /Library/Frameworks/Python.framework
-
-          Homebrew only supports building against the System-provided Python or a
-          brewed Python. In particular, Pythons installed to /Library can interfere
-          with other software installs.
-        EOS
-      end
-
-      def check_for_old_homebrew_share_python_in_path
-        message = ""
-        ["", "3"].map do |suffix|
-          next unless paths.include?((HOMEBREW_PREFIX/"share/python#{suffix}").to_s)
-          message += <<~EOS
-            #{HOMEBREW_PREFIX}/share/python#{suffix} is not needed in PATH.
-          EOS
-        end
-        unless message.empty?
-          message += <<~EOS
-
-            Formerly homebrew put Python scripts you installed via `pip` or `pip3`
-            (or `easy_install`) into that directory above but now it can be removed
-            from your PATH variable.
-            Python scripts will now install into #{HOMEBREW_PREFIX}/bin.
-            You can delete anything, except 'Extras', from the #{HOMEBREW_PREFIX}/share/python
-            (and #{HOMEBREW_PREFIX}/share/python@2) dir and install affected Python packages
-            anew with `pip install --upgrade`.
-          EOS
-        end
-
-        message unless message.empty?
-      end
-
       def check_for_bad_python_symlink
         return unless which "python"
         `python -V 2>&1` =~ /Python (\d+)\./
diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index b50ae317c7..1ed474cfb1 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -22,6 +22,7 @@ class AbstractDownloadStrategy
     @url = resource.url
     @version = resource.version
     @meta = resource.specs
+    @shutup = false
     extend Pourable if meta[:bottle]
   end
 
@@ -80,7 +81,7 @@ class AbstractDownloadStrategy
 
   def safe_system(*args)
     if @shutup
-      quiet_system(*args) || raise(ErrorDuringExecution.new(args.shift, *args))
+      quiet_system(*args) || raise(ErrorDuringExecution.new(args.shift, args))
     else
       super(*args)
     end
@@ -594,6 +595,70 @@ class GitHubPrivateRepositoryReleaseDownloadStrategy < GitHubPrivateRepositoryDo
   end
 end
 
+# ScpDownloadStrategy downloads files using ssh via scp. To use it, add
+# ":using => ScpDownloadStrategy" to the URL section of your formula or
+# provide a URL starting with scp://. This strategy uses ssh credentials for
+# authentication. If a public/private keypair is configured, it will not
+# prompt for a password.
+#
+# Usage:
+#
+#   class Abc < Formula
+#     url "scp://example.com/src/abc.1.0.tar.gz"
+#     ...
+class ScpDownloadStrategy < AbstractFileDownloadStrategy
+  attr_reader :tarball_path, :temporary_path
+
+  def initialize(name, resource)
+    super
+    @tarball_path = HOMEBREW_CACHE/"#{name}-#{version}#{ext}"
+    @temporary_path = Pathname.new("#{cached_location}.incomplete")
+    parse_url_pattern
+  end
+
+  def parse_url_pattern
+    url_pattern = %r{scp://([^@]+@)?([^@:/]+)(:\d+)?/(\S+)}
+    if @url !~ url_pattern
+      raise ScpDownloadStrategyError, "Invalid URL for scp: #{@url}"
+    end
+
+    _, @user, @host, @port, @path = *@url.match(url_pattern)
+  end
+
+  def fetch
+    ohai "Downloading #{@url}"
+
+    if cached_location.exist?
+      puts "Already downloaded: #{cached_location}"
+    else
+      begin
+        safe_system "scp", scp_source, temporary_path.to_s
+      rescue ErrorDuringExecution
+        raise ScpDownloadStrategyError, "Failed to run scp #{scp_source}"
+      end
+
+      ignore_interrupts { temporary_path.rename(cached_location) }
+    end
+  end
+
+  def cached_location
+    tarball_path
+  end
+
+  def clear_cache
+    super
+    rm_rf(temporary_path)
+  end
+
+  private
+
+  def scp_source
+    path_prefix = "/" unless @path.start_with?("~")
+    port_arg = "-P #{@port[1..-1]} " if @port
+    "#{port_arg}#{@user}#{@host}:#{path_prefix}#{@path}"
+  end
+end
+
 class SubversionDownloadStrategy < VCSDownloadStrategy
   def initialize(name, resource)
     super
@@ -1140,6 +1205,8 @@ class DownloadStrategyDetector
     when %r{^s3://}
       require_aws_sdk
       S3DownloadStrategy
+    when %r{^scp://}
+      ScpDownloadStrategy
     else
       CurlDownloadStrategy
     end
diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index b3acf821ec..a33ed47abf 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -515,6 +515,13 @@ class CurlDownloadStrategyError < RuntimeError
   end
 end
 
+# raised in ScpDownloadStrategy.fetch
+class ScpDownloadStrategyError < RuntimeError
+  def initialize(cause)
+    super "Download failed: #{cause}"
+  end
+end
+
 # raised by safe_system in utils.rb
 class ErrorDuringExecution < RuntimeError
   def initialize(cmd, args = [])
diff --git a/Library/Homebrew/extend/ENV/shared.rb b/Library/Homebrew/extend/ENV/shared.rb
index 5a6b779d0e..9ba3a244a4 100644
--- a/Library/Homebrew/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/ENV/shared.rb
@@ -1,7 +1,5 @@
-require "formula"
 require "compilers"
 require "development_tools"
-require "PATH"
 
 # Homebrew extends Ruby's `ENV` to make our code more readable.
 # Implemented in {SharedEnvExtension} and either {Superenv} or
diff --git a/Library/Homebrew/extend/ENV/std.rb b/Library/Homebrew/extend/ENV/std.rb
index 3d082dc837..17e0fd67a0 100644
--- a/Library/Homebrew/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/ENV/std.rb
@@ -13,6 +13,8 @@ module Stdenv
   def setup_build_environment(formula = nil)
     super
 
+    self["HOMEBREW_ENV"] = "std"
+
     PATH.new(ENV["HOMEBREW_PATH"]).each { |p| prepend_path "PATH", p }
 
     # Set the default pkg-config search path, overriding the built-in paths
diff --git a/Library/Homebrew/extend/ENV/super.rb b/Library/Homebrew/extend/ENV/super.rb
index 660b9b3a3c..c9fac5b5cd 100644
--- a/Library/Homebrew/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/ENV/super.rb
@@ -38,6 +38,7 @@ module Superenv
     super
     send(compiler)
 
+    self["HOMEBREW_ENV"] = "super"
     self["MAKEFLAGS"] ||= "-j#{determine_make_jobs}"
     self["PATH"] = determine_path
     self["PKG_CONFIG_PATH"] = determine_pkg_config_path
diff --git a/Library/Homebrew/extend/fileutils.rb b/Library/Homebrew/extend/fileutils.rb
index 6286e48c01..ea2d51c01b 100644
--- a/Library/Homebrew/extend/fileutils.rb
+++ b/Library/Homebrew/extend/fileutils.rb
@@ -1,5 +1,4 @@
 require "fileutils"
-require "tmpdir"
 require "etc"
 
 # Homebrew extends Ruby's `FileUtils` to make our code more readable.
diff --git a/Library/Homebrew/extend/module.rb b/Library/Homebrew/extend/module.rb
index f4ea4de55a..b314543739 100644
--- a/Library/Homebrew/extend/module.rb
+++ b/Library/Homebrew/extend/module.rb
@@ -6,7 +6,9 @@ class Module
     attrs.each do |attr|
       module_eval <<-EOS, file, line
         def #{attr}(val=nil)
-          val.nil? ? @#{attr} : @#{attr} = val
+          @#{attr} ||= nil
+          return @#{attr} if val.nil?
+          @#{attr} = val
         end
       EOS
     end
diff --git a/Library/Homebrew/extend/optparse.rb b/Library/Homebrew/extend/optparse.rb
index 784d6d699d..801f7baddd 100644
--- a/Library/Homebrew/extend/optparse.rb
+++ b/Library/Homebrew/extend/optparse.rb
@@ -1,5 +1,4 @@
 require "optparse"
-require "pathname"
 
 OptionParser.accept Pathname do |path|
   Pathname(path).expand_path if path
diff --git a/Library/Homebrew/extend/os/bottles.rb b/Library/Homebrew/extend/os/bottles.rb
index 146b807a4a..6ee9a2146e 100644
--- a/Library/Homebrew/extend/os/bottles.rb
+++ b/Library/Homebrew/extend/os/bottles.rb
@@ -1,2 +1 @@
-require "utils/bottles"
 require "extend/os/mac/utils/bottles" if OS.mac?
diff --git a/Library/Homebrew/extend/os/dependency_collector.rb b/Library/Homebrew/extend/os/dependency_collector.rb
index 56fcad31d0..10131c916d 100644
--- a/Library/Homebrew/extend/os/dependency_collector.rb
+++ b/Library/Homebrew/extend/os/dependency_collector.rb
@@ -1,2 +1 @@
-require "dependency_collector"
 require "extend/os/mac/dependency_collector" if OS.mac?
diff --git a/Library/Homebrew/extend/os/development_tools.rb b/Library/Homebrew/extend/os/development_tools.rb
index 5bd5cb81a0..2d748074d1 100644
--- a/Library/Homebrew/extend/os/development_tools.rb
+++ b/Library/Homebrew/extend/os/development_tools.rb
@@ -1,2 +1 @@
-require "development_tools"
 require "extend/os/mac/development_tools" if OS.mac?
diff --git a/Library/Homebrew/extend/os/diagnostic.rb b/Library/Homebrew/extend/os/diagnostic.rb
index f8f53b1f4f..3e0d104fc4 100644
--- a/Library/Homebrew/extend/os/diagnostic.rb
+++ b/Library/Homebrew/extend/os/diagnostic.rb
@@ -1,2 +1 @@
-require "diagnostic"
 require "extend/os/mac/diagnostic" if OS.mac?
diff --git a/Library/Homebrew/extend/os/emoji.rb b/Library/Homebrew/extend/os/emoji.rb
index 8fd99e1d3e..59efced1d7 100644
--- a/Library/Homebrew/extend/os/emoji.rb
+++ b/Library/Homebrew/extend/os/emoji.rb
@@ -1,3 +1 @@
-require "os"
-require "emoji"
 require "extend/os/mac/emoji" if OS.mac?
diff --git a/Library/Homebrew/extend/os/extend/ENV/shared.rb b/Library/Homebrew/extend/os/extend/ENV/shared.rb
index e9574eb583..405c442912 100644
--- a/Library/Homebrew/extend/os/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/shared.rb
@@ -1,2 +1 @@
-require "extend/ENV/shared"
 require "extend/os/mac/extend/ENV/shared" if OS.mac?
diff --git a/Library/Homebrew/extend/os/extend/ENV/std.rb b/Library/Homebrew/extend/os/extend/ENV/std.rb
index 18ede5b9ed..7d117c626e 100644
--- a/Library/Homebrew/extend/os/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/std.rb
@@ -1,4 +1,3 @@
-require "extend/ENV/std"
 if OS.mac?
   require "extend/os/mac/extend/ENV/std"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/extend/ENV/super.rb b/Library/Homebrew/extend/os/extend/ENV/super.rb
index 27c49eb849..a04f559f23 100644
--- a/Library/Homebrew/extend/os/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/os/extend/ENV/super.rb
@@ -1,2 +1 @@
-require "extend/ENV/super"
 require "extend/os/mac/extend/ENV/super" if OS.mac?
diff --git a/Library/Homebrew/extend/os/formula_cellar_checks.rb b/Library/Homebrew/extend/os/formula_cellar_checks.rb
index 66b5b80d3d..7198179563 100644
--- a/Library/Homebrew/extend/os/formula_cellar_checks.rb
+++ b/Library/Homebrew/extend/os/formula_cellar_checks.rb
@@ -1,2 +1 @@
-require "formula_cellar_checks"
 require "extend/os/mac/formula_cellar_checks" if OS.mac?
diff --git a/Library/Homebrew/extend/os/keg_relocate.rb b/Library/Homebrew/extend/os/keg_relocate.rb
index 25a74286a4..7c805a7ae1 100644
--- a/Library/Homebrew/extend/os/keg_relocate.rb
+++ b/Library/Homebrew/extend/os/keg_relocate.rb
@@ -1,2 +1 @@
-require "keg_relocate"
 require "extend/os/mac/keg_relocate" if OS.mac?
diff --git a/Library/Homebrew/extend/os/mac/caveats.rb b/Library/Homebrew/extend/os/mac/caveats.rb
index d912a83075..7ddfb5fb4d 100644
--- a/Library/Homebrew/extend/os/mac/caveats.rb
+++ b/Library/Homebrew/extend/os/mac/caveats.rb
@@ -1,4 +1,6 @@
 class Caveats
+  undef plist_caveats
+
   def plist_caveats
     s = []
     if f.plist || (keg&.plist_installed?)
diff --git a/Library/Homebrew/extend/os/mac/cleaner.rb b/Library/Homebrew/extend/os/mac/cleaner.rb
index 74f627b48e..69d82814d7 100644
--- a/Library/Homebrew/extend/os/mac/cleaner.rb
+++ b/Library/Homebrew/extend/os/mac/cleaner.rb
@@ -1,6 +1,8 @@
 class Cleaner
   private
 
+  undef executable_path?
+
   def executable_path?(path)
     path.mach_o_executable? || path.text_executable?
   end
diff --git a/Library/Homebrew/extend/os/mac/dependency_collector.rb b/Library/Homebrew/extend/os/mac/dependency_collector.rb
index a7e5d7ffc8..543c2494ec 100644
--- a/Library/Homebrew/extend/os/mac/dependency_collector.rb
+++ b/Library/Homebrew/extend/os/mac/dependency_collector.rb
@@ -1,6 +1,10 @@
 require "os/mac/ld64_dependency"
 
 class DependencyCollector
+  undef git_dep_if_needed, subversion_dep_if_needed, cvs_dep_if_needed,
+        xz_dep_if_needed, unzip_dep_if_needed, bzip2_dep_if_needed,
+        ld64_dep_if_needed
+
   def git_dep_if_needed(tags)
     return if MacOS.version >= :lion
     Dependency.new("git", tags)
@@ -18,7 +22,7 @@ class DependencyCollector
     Dependency.new("xz", tags)
   end
 
-  def zip_dep_if_needed(tags); end
+  def unzip_dep_if_needed(tags); end
 
   def bzip2_dep_if_needed(tags); end
 
diff --git a/Library/Homebrew/extend/os/mac/development_tools.rb b/Library/Homebrew/extend/os/mac/development_tools.rb
index d37e778ca5..ab2cfe90ea 100644
--- a/Library/Homebrew/extend/os/mac/development_tools.rb
+++ b/Library/Homebrew/extend/os/mac/development_tools.rb
@@ -3,10 +3,13 @@ require "os/mac/xcode"
 # @private
 class DevelopmentTools
   class << self
-    alias original_locate locate
+    alias generic_locate locate
+    undef installed?, default_compiler, curl_handles_most_https_certificates?,
+          subversion_handles_most_https_certificates?
+
     def locate(tool)
       (@locate ||= {}).fetch(tool) do |key|
-        @locate[key] = if (located_tool = original_locate(tool))
+        @locate[key] = if (located_tool = generic_locate(tool))
           located_tool
         elsif MacOS.version > :tiger
           path = Utils.popen_read("/usr/bin/xcrun", "-no-cache", "-find", tool, err: :close).chomp
@@ -22,6 +25,35 @@ class DevelopmentTools
       MacOS::Xcode.installed? || MacOS::CLT.installed?
     end
 
+    def default_compiler
+      case default_cc
+      # if GCC 4.2 is installed, e.g. via Tigerbrew, prefer it
+      # over the system's GCC 4.0
+      when /^gcc-4\.0/ then gcc_4_2_build_version ? :gcc_4_2 : :gcc_4_0
+      when /^gcc/ then :gcc_4_2
+      when "clang" then :clang
+      else
+        # guess :(
+        if MacOS::Xcode.version >= "4.3"
+          :clang
+        else
+          :gcc_4_2
+        end
+      end
+    end
+
+    def curl_handles_most_https_certificates?
+      # The system Curl is too old for some modern HTTPS certificates on
+      # older macOS versions.
+      ENV["HOMEBREW_SYSTEM_CURL_TOO_OLD"].nil?
+    end
+
+    def subversion_handles_most_https_certificates?
+      # The system Subversion is too old for some HTTPS certificates on
+      # older macOS versions.
+      MacOS.version >= :sierra
+    end
+
     def installation_instructions
       if MacOS.version >= "10.9"
         <<~EOS
@@ -64,34 +96,5 @@ class DevelopmentTools
         EOS
       end
     end
-
-    def default_compiler
-      case default_cc
-      # if GCC 4.2 is installed, e.g. via Tigerbrew, prefer it
-      # over the system's GCC 4.0
-      when /^gcc-4\.0/ then gcc_4_2_build_version ? :gcc_4_2 : :gcc_4_0
-      when /^gcc/ then :gcc_4_2
-      when "clang" then :clang
-      else
-        # guess :(
-        if MacOS::Xcode.version >= "4.3"
-          :clang
-        else
-          :gcc_4_2
-        end
-      end
-    end
-
-    def curl_handles_most_https_certificates?
-      # The system Curl is too old for some modern HTTPS certificates on
-      # older macOS versions.
-      ENV["HOMEBREW_SYSTEM_CURL_TOO_OLD"].nil?
-    end
-
-    def subversion_handles_most_https_certificates?
-      # The system Subversion is too old for some HTTPS certificates on
-      # older macOS versions.
-      MacOS.version >= :sierra
-    end
   end
 end
diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index bb89b2367f..92fb3f315f 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -1,14 +1,14 @@
 module Homebrew
   module Diagnostic
     class Checks
+      undef development_tools_checks, fatal_development_tools_checks,
+            build_error_checks
+
       def development_tools_checks
         %w[
           check_for_unsupported_macos
-          check_for_bad_install_name_tool
           check_for_installed_developer_tools
           check_xcode_license_approved
-          check_for_osx_gcc_installer
-          check_xcode_8_without_clt_on_el_capitan
           check_xcode_up_to_date
           check_clt_up_to_date
           check_for_other_package_managers
@@ -92,20 +92,6 @@ module Homebrew
         EOS
       end
 
-      def check_xcode_8_without_clt_on_el_capitan
-        return unless MacOS::Xcode.without_clt?
-        # Scope this to Xcode 8 on El Cap for now
-        return unless MacOS.version == :el_capitan
-        return unless MacOS::Xcode.version >= "8"
-
-        <<~EOS
-          You have Xcode 8 installed without the CLT;
-          this causes certain builds to fail on OS X El Capitan (10.11).
-          Please install the CLT via:
-            sudo xcode-select --install
-        EOS
-      end
-
       def check_xcode_minimum_version
         return unless MacOS::Xcode.below_minimum_version?
 
@@ -134,57 +120,6 @@ module Homebrew
         EOS
       end
 
-      def check_for_osx_gcc_installer
-        return unless MacOS.version < "10.7" || ((MacOS::Xcode.version || "0") > "4.1")
-        return unless DevelopmentTools.clang_version == "2.1"
-
-        fix_advice = if MacOS.version >= :mavericks
-          "Please run `xcode-select --install` to install the CLT."
-        elsif MacOS.version >= :lion
-          "Please install the CLT or Xcode #{MacOS::Xcode.latest_version}."
-        else
-          "Please install Xcode #{MacOS::Xcode.latest_version}."
-        end
-
-        <<~EOS
-          You seem to have osx-gcc-installer installed.
-          Homebrew doesn't support osx-gcc-installer. It causes many builds to fail and
-          is an unlicensed distribution of really old Xcode files.
-          #{fix_advice}
-        EOS
-      end
-
-      def check_for_stray_developer_directory
-        # if the uninstaller script isn't there, it's a good guess neither are
-        # any troublesome leftover Xcode files
-        uninstaller = Pathname.new("/Developer/Library/uninstall-developer-folder")
-        return unless ((MacOS::Xcode.version || "0") >= "4.3") && uninstaller.exist?
-
-        <<~EOS
-          You have leftover files from an older version of Xcode.
-          You should delete them using:
-            #{uninstaller}
-        EOS
-      end
-
-      def check_for_bad_install_name_tool
-        return if MacOS.version < "10.9"
-
-        libs = Pathname.new("/usr/bin/install_name_tool").dynamically_linked_libraries
-
-        # otool may not work, for example if the Xcode license hasn't been accepted yet
-        return if libs.empty?
-        return if libs.include? "/usr/lib/libxcselect.dylib"
-
-        <<~EOS
-          You have an outdated version of /usr/bin/install_name_tool installed.
-          This will cause binary package installations to fail.
-          This can happen if you install osx-gcc-installer or RailsInstaller.
-          To restore it, you must reinstall macOS or restore the binary from
-          the OS packages.
-        EOS
-      end
-
       def check_for_other_package_managers
         ponk = MacOS.macports_or_fink
         return if ponk.empty?
@@ -340,33 +275,6 @@ module Homebrew
           may not build correctly with a non-/usr/local prefix.
         EOS
       end
-
-      def check_which_pkg_config
-        binary = which "pkg-config"
-        return if binary.nil?
-
-        mono_config = Pathname.new("/usr/bin/pkg-config")
-        if mono_config.exist? && mono_config.realpath.to_s.include?("Mono.framework")
-          <<~EOS
-            You have a non-Homebrew 'pkg-config' in your PATH:
-              /usr/bin/pkg-config => #{mono_config.realpath}
-
-            This was most likely created by the Mono installer. `./configure` may
-            have problems finding brew-installed packages using this other pkg-config.
-
-            Mono no longer installs this file as of 3.0.4. You should
-            `sudo rm /usr/bin/pkg-config` and upgrade to the latest version of Mono.
-          EOS
-        elsif binary.to_s != "#{HOMEBREW_PREFIX}/bin/pkg-config"
-          <<~EOS
-            You have a non-Homebrew 'pkg-config' in your PATH:
-              #{binary}
-
-            `./configure` may have problems finding brew-installed packages using
-            this other pkg-config.
-          EOS
-        end
-      end
     end
   end
 end
diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/std.rb b/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
index 1a6d10f3b6..370bea2cf2 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/std.rb
@@ -1,5 +1,39 @@
 module Stdenv
   # @private
+
+  undef homebrew_extra_pkg_config_paths, x11
+
+  def homebrew_extra_pkg_config_paths
+    ["#{HOMEBREW_LIBRARY}/Homebrew/os/mac/pkgconfig/#{MacOS.version}"]
+  end
+
+  def x11
+    # There are some config scripts here that should go in the PATH
+    append_path "PATH", MacOS::X11.bin.to_s
+
+    # Append these to PKG_CONFIG_LIBDIR so they are searched
+    # *after* our own pkgconfig directories, as we dupe some of the
+    # libs in XQuartz.
+    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.lib}/pkgconfig"
+    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.share}/pkgconfig"
+
+    append "LDFLAGS", "-L#{MacOS::X11.lib}"
+    append_path "CMAKE_PREFIX_PATH", MacOS::X11.prefix.to_s
+    append_path "CMAKE_INCLUDE_PATH", MacOS::X11.include.to_s
+    append_path "CMAKE_INCLUDE_PATH", "#{MacOS::X11.include}/freetype2"
+
+    append "CPPFLAGS", "-I#{MacOS::X11.include}"
+    append "CPPFLAGS", "-I#{MacOS::X11.include}/freetype2"
+
+    append_path "ACLOCAL_PATH", "#{MacOS::X11.share}/aclocal"
+
+    if MacOS::XQuartz.provided_by_apple? && !MacOS::CLT.installed?
+      append_path "CMAKE_PREFIX_PATH", "#{MacOS.sdk_path}/usr/X11"
+    end
+
+    append "CFLAGS", "-I#{MacOS::X11.include}" unless MacOS::CLT.installed?
+  end
+
   def setup_build_environment(formula = nil)
     generic_setup_build_environment formula
 
@@ -29,10 +63,6 @@ module Stdenv
     ld64 if Formula["ld64"].installed?
   end
 
-  def homebrew_extra_pkg_config_paths
-    ["#{HOMEBREW_LIBRARY}/Homebrew/os/mac/pkgconfig/#{MacOS.version}"]
-  end
-
   # Sets architecture-specific flags for every environment variable
   # given in the list `flags`.
   # @private
@@ -110,33 +140,6 @@ module Stdenv
     end
   end
 
-  def x11
-    # There are some config scripts here that should go in the PATH
-    append_path "PATH", MacOS::X11.bin.to_s
-
-    # Append these to PKG_CONFIG_LIBDIR so they are searched
-    # *after* our own pkgconfig directories, as we dupe some of the
-    # libs in XQuartz.
-    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.lib}/pkgconfig"
-    append_path "PKG_CONFIG_LIBDIR", "#{MacOS::X11.share}/pkgconfig"
-
-    append "LDFLAGS", "-L#{MacOS::X11.lib}"
-    append_path "CMAKE_PREFIX_PATH", MacOS::X11.prefix.to_s
-    append_path "CMAKE_INCLUDE_PATH", MacOS::X11.include.to_s
-    append_path "CMAKE_INCLUDE_PATH", "#{MacOS::X11.include}/freetype2"
-
-    append "CPPFLAGS", "-I#{MacOS::X11.include}"
-    append "CPPFLAGS", "-I#{MacOS::X11.include}/freetype2"
-
-    append_path "ACLOCAL_PATH", "#{MacOS::X11.share}/aclocal"
-
-    if MacOS::XQuartz.provided_by_apple? && !MacOS::CLT.installed?
-      append_path "CMAKE_PREFIX_PATH", "#{MacOS.sdk_path}/usr/X11"
-    end
-
-    append "CFLAGS", "-I#{MacOS::X11.include}" unless MacOS::CLT.installed?
-  end
-
   def no_weak_imports
     append "LDFLAGS", "-Wl,-no_weak_imports" if no_weak_imports_support?
   end
diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
index f233002ea0..c60c9ab193 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
@@ -1,16 +1,24 @@
 module Superenv
+  class << self
+    undef bin
+
+    # @private
+    def bin
+      return unless DevelopmentTools.installed?
+
+      (HOMEBREW_SHIMS_PATH/"super").realpath
+    end
+  end
+
   alias x11? x11
 
-  # @private
-  def self.bin
-    return unless DevelopmentTools.installed?
-
-    (HOMEBREW_SHIMS_PATH/"super").realpath
-  end
-
-  def effective_sysroot
-    MacOS.sdk_path.to_s if MacOS::Xcode.without_clt?
-  end
+  undef homebrew_extra_paths,
+        homebrew_extra_pkg_config_paths, homebrew_extra_aclocal_paths,
+        homebrew_extra_isystem_paths, homebrew_extra_library_paths,
+        homebrew_extra_cmake_include_paths,
+        homebrew_extra_cmake_library_paths,
+        homebrew_extra_cmake_frameworks_paths,
+        determine_cccfg, set_x11_env_if_installed
 
   def homebrew_extra_paths
     paths = []
@@ -86,6 +94,14 @@ module Superenv
     s
   end
 
+  def effective_sysroot
+    MacOS.sdk_path.to_s if MacOS::Xcode.without_clt?
+  end
+
+  def set_x11_env_if_installed
+    ENV.x11 = MacOS::X11.installed?
+  end
+
   # @private
   def setup_build_environment(formula = nil)
     generic_setup_build_environment(formula)
@@ -115,10 +131,6 @@ module Superenv
     self["HOMEBREW_PREFER_CLT_PROXIES"] = "1" if MacOS.version >= "10.9"
   end
 
-  def set_x11_env_if_installed
-    ENV.x11 = MacOS::X11.installed?
-  end
-
   def no_weak_imports
     append "HOMEBREW_CCCFG", "w" if no_weak_imports_support?
   end
diff --git a/Library/Homebrew/extend/os/mac/formula_cellar_checks.rb b/Library/Homebrew/extend/os/mac/formula_cellar_checks.rb
index 0b1a1643e1..1b43b0448b 100644
--- a/Library/Homebrew/extend/os/mac/formula_cellar_checks.rb
+++ b/Library/Homebrew/extend/os/mac/formula_cellar_checks.rb
@@ -66,10 +66,10 @@ module FormulaCellarChecks
     keg = Keg.new(formula.prefix)
     checker = LinkageChecker.new(keg, formula)
 
-    return unless checker.broken_dylibs?
+    return unless checker.broken_library_linkage?
     output = <<~EOS
       #{formula} has broken dynamic library links:
-        #{checker.broken_dylibs.to_a * "\n  "}
+        #{checker.display_test_output}
     EOS
     tab = Tab.for_keg(keg)
     if tab.poured_from_bottle
diff --git a/Library/Homebrew/extend/os/mac/hardware/cpu.rb b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
index cc41ae9112..340e421221 100644
--- a/Library/Homebrew/extend/os/mac/hardware/cpu.rb
+++ b/Library/Homebrew/extend/os/mac/hardware/cpu.rb
@@ -1,6 +1,9 @@
 module Hardware
   class CPU
     class << self
+      undef optimization_flags, type, family, universal_archs, can_run?,
+            features, sse4?
+
       PPC_OPTIMIZATION_FLAGS = {
         g3: "-mcpu=750",
         g4: "-mcpu=7400",
@@ -8,6 +11,7 @@ module Hardware
         g5: "-mcpu=970",
         g5_64: "-mcpu=970 -arch ppc64",
       }.freeze
+
       def optimization_flags
         OPTIMIZATION_FLAGS.merge(PPC_OPTIMIZATION_FLAGS)
       end
@@ -71,10 +75,6 @@ module Hardware
         end
       end
 
-      def extmodel
-        sysctl_int("machdep.cpu.extmodel")
-      end
-
       # Returns an array that's been extended with ArchitectureListExtension,
       # which provides helpers like #as_arch_flags and #as_cmake_arch_flags.
       def universal_archs
@@ -113,6 +113,14 @@ module Hardware
         ).split(" ").map { |s| s.downcase.to_sym }
       end
 
+      def sse4?
+        sysctl_bool("hw.optional.sse4_1")
+      end
+
+      def extmodel
+        sysctl_int("machdep.cpu.extmodel")
+      end
+
       def aes?
         sysctl_bool("hw.optional.aes")
       end
@@ -137,10 +145,6 @@ module Hardware
         sysctl_bool("hw.optional.supplementalsse3")
       end
 
-      def sse4?
-        sysctl_bool("hw.optional.sse4_1")
-      end
-
       def sse4_2?
         sysctl_bool("hw.optional.sse4_2")
       end
@@ -163,15 +167,15 @@ module Hardware
 
       def intel_can_run?(arch)
         case arch
-        when :ppc
+        when *PPC_32BIT_ARCHS
           # Rosetta is still available
           MacOS.version < :lion
-        when :ppc64
+        when *PPC_64BIT_ARCHS
           # Rosetta never supported PPC64
           false
-        when :x86_64
+        when *INTEL_64BIT_ARCHS
           Hardware::CPU.is_64_bit?
-        when :i386
+        when *INTEL_32BIT_ARCHS
           true
         else # dunno
           false
@@ -180,9 +184,9 @@ module Hardware
 
       def ppc_can_run?(arch)
         case arch
-        when :ppc
+        when *PPC_32BIT_ARCHS
           true
-        when :ppc64
+        when *PPC_64BIT_ARCHS
           Hardware::CPU.is_64_bit?
         else
           # Intel is never supported
diff --git a/Library/Homebrew/extend/os/mac/keg_relocate.rb b/Library/Homebrew/extend/os/mac/keg_relocate.rb
index 707710be61..f92134e5a4 100644
--- a/Library/Homebrew/extend/os/mac/keg_relocate.rb
+++ b/Library/Homebrew/extend/os/mac/keg_relocate.rb
@@ -1,24 +1,20 @@
 class Keg
-  def fix_dynamic_linkage
-    mach_o_files.each do |file|
-      file.ensure_writable do
-        change_dylib_id(dylib_id_for(file), file) if file.dylib?
+  class << self
+    undef file_linked_libraries
 
-        each_install_name_for(file) do |bad_name|
-          # Don't fix absolute paths unless they are rooted in the build directory
-          next if bad_name.start_with?("/") &&
-                  !bad_name.start_with?(HOMEBREW_TEMP.to_s) &&
-                  !bad_name.start_with?(HOMEBREW_TEMP.realpath.to_s)
-
-          new_name = fixed_name(file, bad_name)
-          change_install_name(bad_name, new_name, file) unless new_name == bad_name
-        end
+    def file_linked_libraries(file, string)
+      # Check dynamic library linkage. Importantly, do not perform for static
+      # libraries, which will falsely report "linkage" to themselves.
+      if file.mach_o_executable? || file.dylib? || file.mach_o_bundle?
+        file.dynamically_linked_libraries.select { |lib| lib.include? string }
+      else
+        []
       end
     end
-
-    generic_fix_dynamic_linkage
   end
 
+  undef relocate_dynamic_linkage, detect_cxx_stdlibs
+
   def relocate_dynamic_linkage(relocation)
     mach_o_files.each do |file|
       file.ensure_writable do
@@ -58,6 +54,26 @@ class Keg
     results.to_a
   end
 
+  def fix_dynamic_linkage
+    mach_o_files.each do |file|
+      file.ensure_writable do
+        change_dylib_id(dylib_id_for(file), file) if file.dylib?
+
+        each_install_name_for(file) do |bad_name|
+          # Don't fix absolute paths unless they are rooted in the build directory
+          next if bad_name.start_with?("/") &&
+                  !bad_name.start_with?(HOMEBREW_TEMP.to_s) &&
+                  !bad_name.start_with?(HOMEBREW_TEMP.realpath.to_s)
+
+          new_name = fixed_name(file, bad_name)
+          change_install_name(bad_name, new_name, file) unless new_name == bad_name
+        end
+      end
+    end
+
+    generic_fix_dynamic_linkage
+  end
+
   # If file is a dylib or bundle itself, look for the dylib named by
   # bad_name relative to the lib directory, so that we can skip the more
   # expensive recursive search if possible.
@@ -130,14 +146,4 @@ class Keg
     # it's wrong. -O is a BSD-grep-only option.
     "-lrO"
   end
-
-  def self.file_linked_libraries(file, string)
-    # Check dynamic library linkage. Importantly, do not perform for static
-    # libraries, which will falsely report "linkage" to themselves.
-    if file.mach_o_executable? || file.dylib? || file.mach_o_bundle?
-      file.dynamically_linked_libraries.select { |lib| lib.include? string }
-    else
-      []
-    end
-  end
 end
diff --git a/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
index b8cf502a5e..b561d3c7af 100644
--- a/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
+++ b/Library/Homebrew/extend/os/mac/requirements/java_requirement.rb
@@ -4,26 +4,9 @@ class JavaRequirement < Requirement
     env_oracle_jdk || env_apple
   end
 
-  # A strict Java 8 requirement (1.8) should prompt the user to install
-  # the legacy java8 cask because versions newer than Java 8 are not
-  # completely backwards compatible, and contain breaking changes such as
-  # strong encapsulation of JDK-internal APIs and a modified version scheme
-  # (*.0 not 1.*).
-  def cask
-    if @version.nil? || @version.to_s.end_with?("+") ||
-       @version.to_f >= JAVA_CASK_MAP.keys.max.to_f
-      JAVA_CASK_MAP.fetch(JAVA_CASK_MAP.keys.max)
-    else
-      JAVA_CASK_MAP.fetch("1.8")
-    end
-  end
-
   private
 
-  JAVA_CASK_MAP = {
-    "1.8" => "caskroom/versions/java8",
-    "10.0" => "java",
-  }.freeze
+  undef possible_javas, oracle_java_os
 
   def possible_javas
     javas = []
@@ -35,6 +18,10 @@ class JavaRequirement < Requirement
     javas
   end
 
+  def oracle_java_os
+    :darwin
+  end
+
   def java_home_cmd
     return nil unless File.executable?("/usr/libexec/java_home")
     args = %w[--failfast]
@@ -47,8 +34,4 @@ class JavaRequirement < Requirement
   def env_apple
     ENV.append_to_cflags "-I/System/Library/Frameworks/JavaVM.framework/Versions/Current/Headers/"
   end
-
-  def oracle_java_os
-    :darwin
-  end
 end
diff --git a/Library/Homebrew/extend/os/mac/requirements/non_binary_osxfuse_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/non_binary_osxfuse_requirement.rb
new file mode 100644
index 0000000000..39d638cf88
--- /dev/null
+++ b/Library/Homebrew/extend/os/mac/requirements/non_binary_osxfuse_requirement.rb
@@ -0,0 +1,15 @@
+require "requirement"
+
+class NonBinaryOsxfuseRequirement < Requirement
+  fatal true
+  satisfy(build_env: false) do
+    HOMEBREW_PREFIX.to_s != "/usr/local" || !OsxfuseRequirement.binary_osxfuse_installed?
+  end
+
+  def message
+    <<~EOS
+      osxfuse is already installed from the binary distribution and
+      conflicts with this formula.
+    EOS
+  end
+end
diff --git a/Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb
index 3f10a951ac..f6ca8cfc28 100644
--- a/Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb
+++ b/Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb
@@ -1,7 +1,6 @@
 require "requirement"
 
 class OsxfuseRequirement < Requirement
-  cask "osxfuse"
   download "https://osxfuse.github.io/"
 
   satisfy(build_env: false) { self.class.binary_osxfuse_installed? }
@@ -20,15 +19,3 @@ class OsxfuseRequirement < Requirement
     end
   end
 end
-
-class NonBinaryOsxfuseRequirement < Requirement
-  fatal true
-  satisfy(build_env: false) { HOMEBREW_PREFIX.to_s != "/usr/local" || !OsxfuseRequirement.binary_osxfuse_installed? }
-
-  def message
-    <<~EOS
-      osxfuse is already installed from the binary distribution and
-      conflicts with this formula.
-    EOS
-  end
-end
diff --git a/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
index 0c319d1de3..91fec032c3 100644
--- a/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
+++ b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
@@ -1,18 +1,17 @@
 require "requirement"
 
 class X11Requirement < Requirement
-  cask "xquartz"
-  download "https://xquartz.macosforge.org"
-
-  def min_version
-    MacOS::XQuartz.minimum_version
-  end
-
   satisfy build_env: false do
     next false unless MacOS::XQuartz.installed?
     min_version <= MacOS::XQuartz.version
   end
 
+  undef min_version, message
+
+  def min_version
+    MacOS::XQuartz.minimum_version
+  end
+
   def message
     "XQuartz #{min_version} (or newer) is required to install this formula. #{super}"
   end
diff --git a/Library/Homebrew/extend/os/mac/system_config.rb b/Library/Homebrew/extend/os/mac/system_config.rb
index c0a28d3e95..20f04c0abd 100644
--- a/Library/Homebrew/extend/os/mac/system_config.rb
+++ b/Library/Homebrew/extend/os/mac/system_config.rb
@@ -1,27 +1,6 @@
 class SystemConfig
   class << self
-    def xcode
-      if instance_variable_defined?(:@xcode)
-        @xcode
-      elsif MacOS::Xcode.installed?
-        @xcode = MacOS::Xcode.version.to_s
-        @xcode += " => #{MacOS::Xcode.prefix}" unless MacOS::Xcode.default_prefix?
-        @xcode
-      end
-    end
-
-    def clt
-      if instance_variable_defined?(:@clt)
-        @clt
-      elsif MacOS::CLT.installed? && MacOS::Xcode.version >= "4.3"
-        @clt = MacOS::CLT.version
-      end
-    end
-
-    def macports_or_fink
-      @ponk ||= MacOS.macports_or_fink
-      @ponk.join(", ") unless @ponk.empty?
-    end
+    undef describe_java, describe_homebrew_ruby
 
     def describe_java
       # java_home doesn't exist on all macOSs; it might be missing on older versions.
@@ -36,11 +15,6 @@ class SystemConfig
       javas.uniq.join(", ")
     end
 
-    def describe_xquartz
-      return "N/A" unless MacOS::XQuartz.installed?
-      "#{MacOS::XQuartz.version} => #{describe_path(MacOS::XQuartz.prefix)}"
-    end
-
     def describe_homebrew_ruby
       s = describe_homebrew_ruby_version
 
@@ -51,13 +25,32 @@ class SystemConfig
       end
     end
 
+    def xcode
+      @xcode ||= if MacOS::Xcode.installed?
+        xcode = MacOS::Xcode.version.to_s
+        xcode += " => #{MacOS::Xcode.prefix}" unless MacOS::Xcode.default_prefix?
+        xcode
+      end
+    end
+
+    def clt
+      @clt ||= if MacOS::CLT.installed? && MacOS::Xcode.version >= "4.3"
+        MacOS::CLT.version
+      end
+    end
+
+    def xquartz
+      @xquartz ||= if MacOS::XQuartz.installed?
+        "#{MacOS::XQuartz.version} => #{describe_path(MacOS::XQuartz.prefix)}"
+      end
+    end
+
     def dump_verbose_config(f = $stdout)
       dump_generic_verbose_config(f)
       f.puts "macOS: #{MacOS.full_version}-#{kernel}"
-      f.puts "Xcode: #{xcode ? xcode : "N/A"}"
       f.puts "CLT: #{clt ? clt : "N/A"}"
-      f.puts "X11: #{describe_xquartz}"
-      f.puts "MacPorts/Fink: #{macports_or_fink}" if macports_or_fink
+      f.puts "Xcode: #{xcode ? xcode : "N/A"}"
+      f.puts "XQuartz: #{xquartz ? xquartz : "N/A"}"
     end
   end
 end
diff --git a/Library/Homebrew/extend/os/mac/utils/bottles.rb b/Library/Homebrew/extend/os/mac/utils/bottles.rb
index 03980aab0c..80d6afe78a 100644
--- a/Library/Homebrew/extend/os/mac/utils/bottles.rb
+++ b/Library/Homebrew/extend/os/mac/utils/bottles.rb
@@ -1,6 +1,8 @@
 module Utils
   class Bottles
     class << self
+      undef tag
+
       def tag
         if MacOS.version >= :lion
           MacOS.cat
@@ -21,9 +23,10 @@ module Utils
     class Collector
       private
 
-      alias original_find_matching_tag find_matching_tag
+      alias generic_find_matching_tag find_matching_tag
+
       def find_matching_tag(tag)
-        original_find_matching_tag(tag) || find_altivec_tag(tag) || find_or_later_tag(tag)
+        generic_find_matching_tag(tag) || find_altivec_tag(tag) || find_or_later_tag(tag)
       end
 
       # This allows generic Altivec PPC bottles to be supported in some
diff --git a/Library/Homebrew/extend/os/missing_formula.rb b/Library/Homebrew/extend/os/missing_formula.rb
index 02c59f4e4c..c589925764 100644
--- a/Library/Homebrew/extend/os/missing_formula.rb
+++ b/Library/Homebrew/extend/os/missing_formula.rb
@@ -1,2 +1 @@
-require "missing_formula"
 require "extend/os/mac/missing_formula" if OS.mac?
diff --git a/Library/Homebrew/extend/os/requirements/java_requirement.rb b/Library/Homebrew/extend/os/requirements/java_requirement.rb
index b512ada476..673d53079b 100644
--- a/Library/Homebrew/extend/os/requirements/java_requirement.rb
+++ b/Library/Homebrew/extend/os/requirements/java_requirement.rb
@@ -1,5 +1,3 @@
-require "requirements/java_requirement"
-
 if OS.mac?
   require "extend/os/mac/requirements/java_requirement"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/requirements/non_binary_osxfuse_requirement.rb b/Library/Homebrew/extend/os/requirements/non_binary_osxfuse_requirement.rb
new file mode 100644
index 0000000000..099f29382c
--- /dev/null
+++ b/Library/Homebrew/extend/os/requirements/non_binary_osxfuse_requirement.rb
@@ -0,0 +1,3 @@
+if OS.mac?
+  require "extend/os/mac/requirements/non_binary_osxfuse_requirement"
+end
diff --git a/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb b/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
index 5f56d48c4a..ab491aa1e4 100644
--- a/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
+++ b/Library/Homebrew/extend/os/requirements/osxfuse_requirement.rb
@@ -1,5 +1,3 @@
-require "requirements/osxfuse_requirement"
-
 if OS.mac?
   require "extend/os/mac/requirements/osxfuse_requirement"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/os/system_config.rb b/Library/Homebrew/extend/os/system_config.rb
index fec31f1fa6..b80eec5e8e 100644
--- a/Library/Homebrew/extend/os/system_config.rb
+++ b/Library/Homebrew/extend/os/system_config.rb
@@ -1,5 +1,3 @@
-require "system_config"
-
 if OS.mac?
   require "extend/os/mac/system_config"
 elsif OS.linux?
diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index baf47b2764..ec7293496e 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -1,7 +1,5 @@
-require "pathname"
 require "resource"
 require "metafiles"
-require "utils"
 
 module DiskUsageExtension
   def disk_usage
@@ -368,7 +366,7 @@ class Pathname
   unless method_defined?(:/)
     def /(other)
       if !other.respond_to?(:to_str) && !other.respond_to?(:to_path)
-        odeprecated "Pathname#/ with #{other.class}", "a String or a Pathname"
+        odisabled "Pathname#/ with #{other.class}", "a String or a Pathname"
       end
       join(other.to_s)
     end
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index c6af96f6d0..69c60a3d28 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -10,7 +10,6 @@ require "formulary"
 require "software_spec"
 require "install_renamed"
 require "pkg_version"
-require "tap"
 require "keg"
 require "migrator"
 require "linkage_checker"
@@ -174,7 +173,9 @@ class Formula
     @name = name
     @path = path
     @alias_path = alias_path
-    @alias_name = File.basename(alias_path) if alias_path
+    @alias_name = if alias_path
+      File.basename(alias_path)
+    end
     @revision = self.class.revision || 0
     @version_scheme = self.class.version_scheme || 0
 
@@ -204,6 +205,7 @@ class Formula
     @pin = FormulaPin.new(self)
     @follow_installed_alias = true
     @prefix_returns_versioned_prefix = false
+    @oldname_lock = nil
   end
 
   # @private
@@ -1130,7 +1132,7 @@ class Formula
     return false unless old_rack.directory?
     return false if old_rack.subdirs.empty?
 
-    tap == Tab.for_keg(old_rack.subdirs.sort.first).tap
+    tap == Tab.for_keg(old_rack.subdirs.min).tap
   end
 
   # @private
@@ -1293,7 +1295,7 @@ class Formula
 
     # Avoid false positives for clock_gettime support on 10.11.
     # CMake cache entries for other weak symbols may be added here as needed.
-    if MacOS.version == "10.11" && MacOS::Xcode.installed? && MacOS::Xcode.version >= "8.0"
+    if MacOS.version == "10.11" && MacOS::Xcode.version >= "8.0"
       args << "-DHAVE_CLOCK_GETTIME:INTERNAL=0"
     end
 
@@ -1539,10 +1541,10 @@ class Formula
       "desc" => desc,
       "homepage" => homepage,
       "oldname" => oldname,
-      "aliases" => aliases,
+      "aliases" => aliases.sort,
       "versions" => {
         "stable" => stable&.version&.to_s,
-        "bottle" => !bottle.nil?,
+        "bottle" => !bottle_specification.checksums.empty?,
         "devel" => devel&.version&.to_s,
         "head" => head&.version&.to_s,
       },
@@ -2364,7 +2366,7 @@ class Formula
     #   version '4.8.1'
     # end</pre>
     def fails_with(compiler, &block)
-      odeprecated "fails_with :llvm" if compiler == :llvm
+      odisabled "fails_with :llvm" if compiler == :llvm
       specs.each { |spec| spec.fails_with(compiler, &block) }
     end
 
diff --git a/Library/Homebrew/formula_cellar_checks.rb b/Library/Homebrew/formula_cellar_checks.rb
index 471a5ea2fe..91a559dfad 100644
--- a/Library/Homebrew/formula_cellar_checks.rb
+++ b/Library/Homebrew/formula_cellar_checks.rb
@@ -154,6 +154,8 @@ module FormulaCellarChecks
   end
 
   def audit_installed
+    @new_formula ||= false
+
     problem_if_output(check_manpages)
     problem_if_output(check_infopages)
     problem_if_output(check_jars)
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 8c7efc978b..7ed473ee89 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -1,5 +1,4 @@
 require "cxxstdlib"
-require "exceptions"
 require "formula"
 require "keg"
 require "tab"
@@ -59,7 +58,8 @@ class FormulaInstaller
     @invalid_option_names = []
     @requirement_messages = []
     @poured_bottle = false
-    @pour_failed   = false
+    @pour_failed = false
+    @start_time = nil
   end
 
   def self.attempted
diff --git a/Library/Homebrew/formula_support.rb b/Library/Homebrew/formula_support.rb
index d44cf158fb..920db5839d 100644
--- a/Library/Homebrew/formula_support.rb
+++ b/Library/Homebrew/formula_support.rb
@@ -12,57 +12,27 @@ class KegOnlyReason
   end
 
   def valid?
-    case @reason
-    when :provided_pre_mountain_lion
-      MacOS.version < :mountain_lion
-    when :provided_pre_mavericks
-      MacOS.version < :mavericks
-    when :provided_pre_el_capitan
-      MacOS.version < :el_capitan
-    when :provided_pre_high_sierra
-      MacOS.version < :high_sierra
-    when :provided_until_xcode43
-      MacOS::Xcode.installed? && MacOS::Xcode.version < "4.3"
-    when :provided_until_xcode5
-      MacOS::Xcode.installed? && MacOS::Xcode.version < "5.0"
-    else
-      true
-    end
+    true
   end
 
   def to_s
     return @explanation unless @explanation.empty?
 
     case @reason
-    when :versioned_formula then <<~EOS
-      this is an alternate version of another formula
-    EOS
-    when :provided_by_macos then <<~EOS
-      macOS already provides this software and installing another version in
-      parallel can cause all kinds of trouble
-    EOS
-    when :shadowed_by_macos then <<~EOS
-      macOS provides similar software and installing this software in
-      parallel can cause all kinds of trouble
-    EOS
-    when :provided_pre_mountain_lion then <<~EOS
-      macOS already provides this software in versions before Mountain Lion
-    EOS
-    when :provided_pre_mavericks then <<~EOS
-      macOS already provides this software in versions before Mavericks
-    EOS
-    when :provided_pre_el_capitan then <<~EOS
-      macOS already provides this software in versions before El Capitan
-    EOS
-    when :provided_pre_high_sierra then <<~EOS
-      macOS already provides this software in versions before High Sierra
-    EOS
-    when :provided_until_xcode43 then <<~EOS
-      Xcode provides this software prior to version 4.3
-    EOS
-    when :provided_until_xcode5 then <<~EOS
-      Xcode provides this software prior to version 5
-    EOS
+    when :versioned_formula
+      <<~EOS
+        this is an alternate version of another formula
+      EOS
+    when :provided_by_macos
+      <<~EOS
+        macOS already provides this software and installing another version in
+        parallel can cause all kinds of trouble
+      EOS
+    when :shadowed_by_macos
+      <<~EOS
+        macOS provides similar software and installing this software in
+        parallel can cause all kinds of trouble
+      EOS
     else
       @reason
     end.strip
@@ -87,10 +57,7 @@ class BottleDisableReason
   end
 
   def to_s
-    if unneeded?
-      "This formula doesn't require compiling."
-    else
-      @reason
-    end
+    return "This formula doesn't require compiling." if unneeded?
+    @reason
   end
 end
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 5f6ae0723b..508611ac80 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -1,5 +1,4 @@
 require "digest/md5"
-require "tap"
 require "extend/cachable"
 
 # The Formulary is responsible for creating instances of Formula.
diff --git a/Library/Homebrew/global.rb b/Library/Homebrew/global.rb
index 32b5377a0e..5d641f1e26 100644
--- a/Library/Homebrew/global.rb
+++ b/Library/Homebrew/global.rb
@@ -1,20 +1,9 @@
-require "forwardable"
-require "extend/module"
-require "extend/predicable"
-require "extend/fileutils"
-require "extend/pathname"
-require "extend/git_repository"
-require "extend/ARGV"
-require "PATH"
-require "extend/string"
-require "os"
-require "utils"
-require "exceptions"
-require "set"
-require "rbconfig"
-require "official_taps"
-require "pp"
+require "pathname"
 require "English"
+require "ostruct"
+
+require "pp"
+require "extend/ARGV"
 
 ARGV.extend(HomebrewArgvExtension)
 
@@ -23,9 +12,12 @@ HOMEBREW_VERSION = ENV["HOMEBREW_VERSION"]
 HOMEBREW_WWW = "https://brew.sh".freeze
 
 require "config"
+require "extend/git_repository"
 
 HOMEBREW_REPOSITORY.extend(GitRepositoryExtension)
 
+require "rbconfig"
+
 RUBY_PATH = Pathname.new(RbConfig.ruby)
 RUBY_BIN = RUBY_PATH.dirname
 
@@ -33,19 +25,22 @@ HOMEBREW_USER_AGENT_CURL = ENV["HOMEBREW_USER_AGENT_CURL"]
 HOMEBREW_USER_AGENT_RUBY = "#{ENV["HOMEBREW_USER_AGENT"]} ruby/#{RUBY_VERSION}-p#{RUBY_PATCHLEVEL}".freeze
 HOMEBREW_USER_AGENT_FAKE_SAFARI = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/602.4.8 (KHTML, like Gecko) Version/10.0.3 Safari/602.4.8".freeze
 
-require "tap_constants"
+require "extend/fileutils"
 
 module Homebrew
   extend FileUtils
 
   class << self
-    attr_writer :failed
+    attr_writer :failed, :raise_deprecation_exceptions, :auditing, :args
 
     def failed?
+      @failed ||= false
       @failed == true
     end
 
-    attr_writer :raise_deprecation_exceptions, :auditing
+    def args
+      @args ||= OpenStruct.new
+    end
 
     def raise_deprecation_exceptions?
       @raise_deprecation_exceptions == true
@@ -60,7 +55,8 @@ end
 HOMEBREW_PULL_API_REGEX = %r{https://api\.github\.com/repos/([\w-]+)/([\w-]+)?/pulls/(\d+)}
 HOMEBREW_PULL_OR_COMMIT_URL_REGEX = %r[https://github\.com/([\w-]+)/([\w-]+)?/(?:pull/(\d+)|commit/[0-9a-fA-F]{4,40})]
 
-require "compat" unless ARGV.include?("--no-compat") || ENV["HOMEBREW_NO_COMPAT"]
+require "forwardable"
+require "PATH"
 
 ENV["HOMEBREW_PATH"] ||= ENV["PATH"]
 ORIGINAL_PATHS = PATH.new(ENV["HOMEBREW_PATH"]).map do |p|
@@ -88,3 +84,24 @@ HOMEBREW_INTERNAL_COMMAND_ALIASES = {
   "environment" => "--env",
   "--config" => "config",
 }.freeze
+
+require "set"
+
+require "os"
+require "extend/pathname"
+
+require "extend/module"
+require "extend/predicable"
+require "extend/string"
+
+require "constants"
+require "exceptions"
+require "utils"
+
+require "official_taps"
+require "tap"
+require "tap_constants"
+
+if !ARGV.include?("--no-compat") && !ENV["HOMEBREW_NO_COMPAT"]
+  require "compat"
+end
diff --git a/Library/Homebrew/hardware.rb b/Library/Homebrew/hardware.rb
index 0559ae694c..c7756dd3b5 100644
--- a/Library/Homebrew/hardware.rb
+++ b/Library/Homebrew/hardware.rb
@@ -1,10 +1,8 @@
-require "os"
-
 module Hardware
   class CPU
     INTEL_32BIT_ARCHS = [:i386].freeze
     INTEL_64BIT_ARCHS = [:x86_64].freeze
-    PPC_32BIT_ARCHS   = [:ppc, :ppc7400, :ppc7450, :ppc970].freeze
+    PPC_32BIT_ARCHS   = [:ppc, :ppc32, :ppc7400, :ppc7450, :ppc970].freeze
     PPC_64BIT_ARCHS   = [:ppc64].freeze
 
     class << self
@@ -120,9 +118,9 @@ module Hardware
         if is_32_bit?
           arch_32_bit == arch
         elsif intel?
-          [:i386, :x86_64].include? arch
+          (INTEL_32BIT_ARCHS + INTEL_64BIT_ARCHS).include?(arch)
         elsif ppc?
-          [:ppc, :ppc64].include? arch
+          (PPC_32BIT_ARCHS + PPC_64BIT_ARCHS).include?(arch)
         else
           false
         end
diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index 04c98c9556..02e318624b 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -1,4 +1,3 @@
-require "extend/pathname"
 require "keg_relocate"
 require "lock_file"
 require "ostruct"
@@ -130,7 +129,7 @@ class Keg
         f_kegs = kegs_by_source[[f.name, f.tap]]
         next unless f_kegs
 
-        f_kegs.sort_by(&:version).last
+        f_kegs.max_by(&:version)
       end.compact
 
       next if required_kegs.empty?
@@ -238,10 +237,14 @@ class Keg
 
     if tap
       bad_tap_opt = opt/tap.user
-      FileUtils.rm_rf bad_tap_opt if bad_tap_opt.directory?
+      if !bad_tap_opt.symlink? && bad_tap_opt.directory?
+        FileUtils.rm_rf bad_tap_opt
+      end
     end
 
     aliases.each do |a|
+      # versioned aliases are handled below
+      next if a =~ /.+@./
       alias_symlink = opt/a
       if alias_symlink.symlink? && alias_symlink.exist?
         alias_symlink.delete if alias_symlink.realpath == opt_record.realpath
@@ -251,7 +254,7 @@ class Keg
     end
 
     Pathname.glob("#{opt_record}@*").each do |a|
-      a = a.basename
+      a = a.basename.to_s
       next if aliases.include?(a)
 
       alias_symlink = opt/a
diff --git a/Library/Homebrew/keg_relocate.rb b/Library/Homebrew/keg_relocate.rb
index f70bbcbacd..6b996f6708 100644
--- a/Library/Homebrew/keg_relocate.rb
+++ b/Library/Homebrew/keg_relocate.rb
@@ -68,7 +68,7 @@ class Keg
         relocation.old_cellar => relocation.new_cellar,
         relocation.old_repository => relocation.new_repository,
       }
-      changed = s.gsub!(Regexp.union(replacements.keys), replacements)
+      changed = s.gsub!(Regexp.union(replacements.keys.sort_by(&:length).reverse), replacements)
       next unless changed
       changed_files += [first, *rest].map { |file| file.relative_path_from(path) }
 
diff --git a/Library/Homebrew/language/python.rb b/Library/Homebrew/language/python.rb
index de373efda4..171d7e8244 100644
--- a/Library/Homebrew/language/python.rb
+++ b/Library/Homebrew/language/python.rb
@@ -1,4 +1,3 @@
-require "utils"
 require "language/python_virtualenv_constants"
 
 module Language
diff --git a/Library/Homebrew/language/python_virtualenv_constants.rb b/Library/Homebrew/language/python_virtualenv_constants.rb
index 4efd2ce1d1..64d24166c0 100644
--- a/Library/Homebrew/language/python_virtualenv_constants.rb
+++ b/Library/Homebrew/language/python_virtualenv_constants.rb
@@ -1,2 +1,2 @@
-PYTHON_VIRTUALENV_URL = "https://files.pythonhosted.org/packages/d4/0c/9840c08189e030873387a73b90ada981885010dd9aea134d6de30cd24cb8/virtualenv-15.1.0.tar.gz".freeze
-PYTHON_VIRTUALENV_SHA256 = "02f8102c2436bb03b3ee6dede1919d1dac8a427541652e5ec95171ec8adbc93a".freeze
+PYTHON_VIRTUALENV_URL = "https://files.pythonhosted.org/packages/b1/72/2d70c5a1de409ceb3a27ff2ec007ecdd5cc52239e7c74990e32af57affe9/virtualenv-15.2.0.tar.gz".freeze
+PYTHON_VIRTUALENV_SHA256 = "1d7e241b431e7afce47e77f8843a276f652699d1fa4f93b9d8ce0076fd7b0b54".freeze
diff --git a/Library/Homebrew/linkage_checker.rb b/Library/Homebrew/linkage_checker.rb
index f60cca98c1..6984397435 100644
--- a/Library/Homebrew/linkage_checker.rb
+++ b/Library/Homebrew/linkage_checker.rb
@@ -1,18 +1,14 @@
-require "set"
 require "keg"
 require "formula"
 
 class LinkageChecker
-  attr_reader :keg, :formula
-  attr_reader :brewed_dylibs, :system_dylibs, :broken_dylibs, :variable_dylibs
-  attr_reader :undeclared_deps, :unnecessary_deps, :reverse_links
-
   def initialize(keg, formula = nil)
     @keg = keg
     @formula = formula || resolve_formula(keg)
     @brewed_dylibs = Hash.new { |h, k| h[k] = Set.new }
     @system_dylibs = Set.new
-    @broken_dylibs = Set.new
+    @broken_dylibs = []
+    @broken_deps = Hash.new { |h, k| h[k] = [] }
     @variable_dylibs = Set.new
     @indirect_deps = []
     @undeclared_deps = []
@@ -21,7 +17,51 @@ class LinkageChecker
     check_dylibs
   end
 
+  def display_normal_output
+    display_items "System libraries", @system_dylibs
+    display_items "Homebrew libraries", @brewed_dylibs
+    display_items "Indirect dependencies with linkage", @indirect_deps
+    display_items "Variable-referenced libraries", @variable_dylibs
+    display_items "Missing libraries", @broken_dylibs
+    display_items "Broken dependencies", @broken_deps
+    display_items "Undeclared dependencies with linkage", @undeclared_deps
+    display_items "Dependencies with no linkage", @unnecessary_deps
+  end
+
+  def display_reverse_output
+    return if @reverse_links.empty?
+    sorted = @reverse_links.sort
+    sorted.each do |dylib, files|
+      puts dylib
+      files.each do |f|
+        unprefixed = f.to_s.strip_prefix "#{@keg}/"
+        puts "  #{unprefixed}"
+      end
+      puts unless dylib == sorted.last[0]
+    end
+  end
+
+  def display_test_output(puts_output: true)
+    display_items "Missing libraries", @broken_dylibs, puts_output: puts_output
+    display_items "Broken dependencies", @broken_deps, puts_output: puts_output
+    puts "No broken library linkage" unless broken_library_linkage?
+  end
+
+  def broken_library_linkage?
+    !@broken_dylibs.empty? || !@broken_deps.empty?
+  end
+
+  private
+
+  attr_reader :keg, :formula
+
+  def dylib_to_dep(dylib)
+    dylib =~ %r{#{Regexp.escape(HOMEBREW_PREFIX)}/(opt|Cellar)/([\w+-.@]+)/}
+    Regexp.last_match(2)
+  end
+
   def check_dylibs
+    checked_dylibs = Set.new
     @keg.find do |file|
       next if file.symlink? || file.directory?
       next unless file.dylib? || file.binary_executable? || file.mach_o_bundle?
@@ -30,6 +70,7 @@ class LinkageChecker
       # when checking for broken linkage
       file.dynamically_linked_libraries(except: :LC_LOAD_WEAK_DYLIB).each do |dylib|
         @reverse_links[dylib] << file
+        next if checked_dylibs.include? dylib
         if dylib.start_with? "@"
           @variable_dylibs << dylib
         else
@@ -39,7 +80,11 @@ class LinkageChecker
             @system_dylibs << dylib
           rescue Errno::ENOENT
             next if harmless_broken_link?(dylib)
-            @broken_dylibs << dylib
+            if (dep = dylib_to_dep(dylib))
+              @broken_deps[dep] |= [dylib]
+            else
+              @broken_dylibs << dylib
+            end
           else
             tap = Tab.for_keg(owner).tap
             f = if tap.nil? || tap.core_tap?
@@ -50,6 +95,7 @@ class LinkageChecker
             @brewed_dylibs[f] << dylib
           end
         end
+        checked_dylibs << dylib
       end
     end
 
@@ -94,6 +140,9 @@ class LinkageChecker
       @brewed_dylibs.keys.map { |x| x.split("/").last }.include?(name)
     end
 
+    missing_deps = @broken_deps.values.flatten.map { |d| dylib_to_dep(d) }
+    unnecessary_deps -= missing_deps
+    
     [indirect_deps, undeclared_deps, unnecessary_deps]
   end
 
@@ -109,49 +158,6 @@ class LinkageChecker
     end
   end
 
-  def display_normal_output
-    display_items "System libraries", @system_dylibs
-    display_items "Homebrew libraries", @brewed_dylibs
-    display_items "Indirect dependencies with linkage", @indirect_deps
-    display_items "Variable-referenced libraries", @variable_dylibs
-    display_items "Missing libraries", @broken_dylibs
-    display_items "Undeclared dependencies with linkage", @undeclared_deps
-    display_items "Dependencies with no linkage", @unnecessary_deps
-  end
-
-  def display_reverse_output
-    return if @reverse_links.empty?
-    sorted = @reverse_links.sort
-    sorted.each do |dylib, files|
-      puts dylib
-      files.each do |f|
-        unprefixed = f.to_s.strip_prefix "#{@keg}/"
-        puts "  #{unprefixed}"
-      end
-      puts unless dylib == sorted.last[0]
-    end
-  end
-
-  def display_test_output
-    display_items "Missing libraries", @broken_dylibs
-    display_items "Possible unnecessary dependencies", @unnecessary_deps
-    puts "No broken dylib links" if @broken_dylibs.empty?
-  end
-
-  def broken_dylibs?
-    !@broken_dylibs.empty?
-  end
-
-  def undeclared_deps?
-    !@undeclared_deps.empty?
-  end
-
-  def unnecessary_deps?
-    !@unnecessary_deps.empty?
-  end
-
-  private
-
   # Whether or not dylib is a harmless broken link, meaning that it's
   # okay to skip (and not report) as broken.
   def harmless_broken_link?(dylib)
@@ -165,20 +171,22 @@ class LinkageChecker
 
   # Display a list of things.
   # Things may either be an array, or a hash of (label -> array)
-  def display_items(label, things)
+  def display_items(label, things, puts_output: true)
     return if things.empty?
-    puts "#{label}:"
+    output = "#{label}:"
     if things.is_a? Hash
-      things.sort.each do |list_label, list|
-        list.sort.each do |item|
-          puts "  #{item} (#{list_label})"
+      things.keys.sort.each do |list_label|
+        things[list_label].sort.each do |item|
+          output += "\n  #{item} (#{list_label})"
         end
       end
     else
       things.sort.each do |item|
-        puts "  #{item}"
+        output += "\n  #{item}"
       end
     end
+    puts output if puts_output
+    output
   end
 
   def resolve_formula(keg)
diff --git a/Library/Homebrew/manpages/brew.1.md.erb b/Library/Homebrew/manpages/brew.1.md.erb
index a4854cc67c..3d54243a3d 100644
--- a/Library/Homebrew/manpages/brew.1.md.erb
+++ b/Library/Homebrew/manpages/brew.1.md.erb
@@ -102,6 +102,8 @@ can take several different forms:
     The formula file will be cached for later use.
 
 ## ENVIRONMENT
+Note that environment variables must have a value set to be detected. For example, `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just `export HOMEBREW_NO_INSECURE_REDIRECT`.
+
   * `HOMEBREW_ARTIFACT_DOMAIN`:
     If set, instructs Homebrew to use the given URL as a download mirror for bottles and binaries.
 
@@ -136,6 +138,10 @@ can take several different forms:
 
     *Default:* `~/Library/Caches/Homebrew`.
 
+  * `HOMEBREW_CURLRC`:
+    If set, Homebrew will not pass `-q` when invoking `curl`(1) (which disables
+    the use of `curlrc`).
+
   * `HOMEBREW_CURL_VERBOSE`:
     If set, Homebrew will pass `--verbose` when invoking `curl`(1).
 
diff --git a/Library/Homebrew/metafiles.rb b/Library/Homebrew/metafiles.rb
index 96fa086f49..51d64ad8d0 100644
--- a/Library/Homebrew/metafiles.rb
+++ b/Library/Homebrew/metafiles.rb
@@ -1,4 +1,3 @@
-require "set"
 
 module Metafiles
   # https://github.com/github/markup#markups
diff --git a/Library/Homebrew/migrator.rb b/Library/Homebrew/migrator.rb
index 503f889852..9b295c1a43 100644
--- a/Library/Homebrew/migrator.rb
+++ b/Library/Homebrew/migrator.rb
@@ -1,4 +1,3 @@
-require "formula"
 require "lock_file"
 require "keg"
 require "tab"
diff --git a/Library/Homebrew/missing_formula.rb b/Library/Homebrew/missing_formula.rb
index 31dfa94efa..3b4682d668 100644
--- a/Library/Homebrew/missing_formula.rb
+++ b/Library/Homebrew/missing_formula.rb
@@ -1,6 +1,4 @@
 require "formulary"
-require "tap"
-require "utils"
 
 module Homebrew
   module MissingFormula
@@ -95,7 +93,7 @@ module Homebrew
           new_tap = old_tap.tap_migrations[name]
           next unless new_tap
 
-          new_tap_user, new_tap_repo, = new_tap.split("/")
+          new_tap_user, new_tap_repo, new_tap_new_name = new_tap.split("/")
           new_tap_name = "#{new_tap_user}/#{new_tap_repo}"
 
           message = <<~EOS
@@ -103,9 +101,18 @@ module Homebrew
           EOS
           break if new_tap_name == CoreTap.instance.name
 
+          install_cmd = if new_tap_user == "caskroom"
+            "cask install"
+          else
+            "install"
+          end
+          new_tap_new_name ||= name
+
           message += <<~EOS
             You can access it again by running:
               brew tap #{new_tap_name}
+            And then you can install it by running:
+              brew #{install_cmd} #{new_tap_new_name}
           EOS
           break
         end
diff --git a/Library/Homebrew/official_taps.rb b/Library/Homebrew/official_taps.rb
index 7eace302a5..a6c7b00fba 100644
--- a/Library/Homebrew/official_taps.rb
+++ b/Library/Homebrew/official_taps.rb
@@ -1,7 +1,3 @@
-OFFICIAL_TAPS = %w[
-  php
-].freeze
-
 OFFICIAL_CASK_TAPS = %w[
   cask
   versions
@@ -25,6 +21,7 @@ DEPRECATED_OFFICIAL_TAPS = %w[
   gui
   head-only
   nginx
+  php
   python
   science
   tex
diff --git a/Library/Homebrew/options.rb b/Library/Homebrew/options.rb
index 05dd643ffe..11f8df3a54 100644
--- a/Library/Homebrew/options.rb
+++ b/Library/Homebrew/options.rb
@@ -1,4 +1,3 @@
-require "set"
 
 class Option
   attr_reader :name, :description, :flag
diff --git a/Library/Homebrew/os.rb b/Library/Homebrew/os.rb
index cc6c865375..ed12ea734f 100644
--- a/Library/Homebrew/os.rb
+++ b/Library/Homebrew/os.rb
@@ -1,5 +1,3 @@
-require "rbconfig"
-
 module OS
   def self.mac?
     return false if ENV["HOMEBREW_TEST_GENERIC_OS"]
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index ade801c42a..3088dbf265 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -1,5 +1,3 @@
-require "hardware"
-require "development_tools"
 require "os/mac/version"
 require "os/mac/xcode"
 require "os/mac/xquartz"
@@ -211,6 +209,8 @@ module OS
       "9.0"   => { clang: "9.0", clang_build: 900 },
       "9.0.1" => { clang: "9.0", clang_build: 900 },
       "9.1"   => { clang: "9.0", clang_build: 900 },
+      "9.2"   => { clang: "9.0", clang_build: 900 },
+      "9.3"   => { clang: "9.1", clang_build: 902 },
     }.freeze
 
     def compilers_standard?
diff --git a/Library/Homebrew/os/mac/architecture_list.rb b/Library/Homebrew/os/mac/architecture_list.rb
index 6f498c51f6..6373aed44d 100644
--- a/Library/Homebrew/os/mac/architecture_list.rb
+++ b/Library/Homebrew/os/mac/architecture_list.rb
@@ -1,4 +1,4 @@
-require "extend/os/hardware"
+require "hardware"
 
 module ArchitectureListExtension
   # @private
diff --git a/Library/Homebrew/os/mac/xcode.rb b/Library/Homebrew/os/mac/xcode.rb
index 2e4ec63819..f39273b42d 100644
--- a/Library/Homebrew/os/mac/xcode.rb
+++ b/Library/Homebrew/os/mac/xcode.rb
@@ -18,12 +18,12 @@ module OS
         when "10.10" then "7.2.1"
         when "10.11" then "8.2.1"
         when "10.12" then "9.2"
-        when "10.13" then "9.2"
+        when "10.13" then "9.3"
         else
           raise "macOS '#{MacOS.version}' is invalid" unless OS::Mac.prerelease?
 
           # Default to newest known version of Xcode for unreleased macOS versions.
-          "9.2"
+          "9.3"
         end
       end
 
@@ -169,8 +169,9 @@ module OS
         when 73      then "7.3"
         when 80      then "8.0"
         when 81      then "8.3"
-        when 90      then "9.0"
-        else              "9.0"
+        when 90      then "9.2"
+        when 91      then "9.3"
+        else              "9.3"
         end
       end
 
@@ -221,7 +222,7 @@ module OS
         # on the older supported platform for that Xcode release, i.e there's no
         # CLT package for 10.11 that contains the Clang version from Xcode 8.
         case MacOS.version
-        when "10.13" then "900.0.39.2"
+        when "10.13" then "902.0.39.1"
         when "10.12" then "900.0.39.2"
         when "10.11" then "800.0.42.1"
         when "10.10" then "700.1.81"
diff --git a/Library/Homebrew/patch.rb b/Library/Homebrew/patch.rb
index 77021480c4..9150be25e7 100644
--- a/Library/Homebrew/patch.rb
+++ b/Library/Homebrew/patch.rb
@@ -17,6 +17,8 @@ module Patch
       else
         ExternalPatch.new(strip, &block)
       end
+    when nil
+      raise ArgumentError, "nil value for strip"
     else
       raise ArgumentError, "unexpected value #{strip.inspect} for strip"
     end
diff --git a/Library/Homebrew/readall.rb b/Library/Homebrew/readall.rb
index 1b6ae016e0..249987b33b 100644
--- a/Library/Homebrew/readall.rb
+++ b/Library/Homebrew/readall.rb
@@ -1,5 +1,4 @@
 require "formula"
-require "tap"
 
 module Readall
   class << self
diff --git a/Library/Homebrew/requirement.rb b/Library/Homebrew/requirement.rb
index f70746c316..d922a22772 100644
--- a/Library/Homebrew/requirement.rb
+++ b/Library/Homebrew/requirement.rb
@@ -140,7 +140,7 @@ class Requirement
     attr_rw :fatal, :cask, :download
 
     def default_formula(_val = nil)
-      odeprecated "Requirement.default_formula"
+      odisabled "Requirement.default_formula"
     end
 
     def satisfy(options = nil, &block)
diff --git a/Library/Homebrew/requirements/java_requirement.rb b/Library/Homebrew/requirements/java_requirement.rb
index 213203ff39..27348fa8cc 100644
--- a/Library/Homebrew/requirements/java_requirement.rb
+++ b/Library/Homebrew/requirements/java_requirement.rb
@@ -4,6 +4,20 @@ class JavaRequirement < Requirement
   fatal true
   download "https://www.oracle.com/technetwork/java/javase/downloads/index.html"
 
+  # A strict Java 8 requirement (1.8) should prompt the user to install
+  # the legacy java8 cask because versions newer than Java 8 are not
+  # completely backwards compatible, and contain breaking changes such as
+  # strong encapsulation of JDK-internal APIs and a modified version scheme
+  # (*.0 not 1.*).
+  def cask
+    if @version.nil? || @version.to_s.end_with?("+") ||
+       @version.to_f >= JAVA_CASK_MAP.keys.max.to_f
+      JAVA_CASK_MAP.fetch(JAVA_CASK_MAP.keys.max)
+    else
+      JAVA_CASK_MAP.fetch("1.8")
+    end
+  end
+
   satisfy build_env: false do
     setup_java
     next false unless @java
@@ -42,6 +56,11 @@ class JavaRequirement < Requirement
 
   private
 
+  JAVA_CASK_MAP = {
+    "1.8" => "caskroom/versions/java8",
+    "10.0" => "java",
+  }.freeze
+
   def version_without_plus
     if exact_version?
       @version
diff --git a/Library/Homebrew/requirements/non_binary_osxfuse_requirement.rb b/Library/Homebrew/requirements/non_binary_osxfuse_requirement.rb
new file mode 100644
index 0000000000..bb7788f487
--- /dev/null
+++ b/Library/Homebrew/requirements/non_binary_osxfuse_requirement.rb
@@ -0,0 +1,7 @@
+require "requirement"
+
+class NonBinaryOsxfuseRequirement < Requirement
+  fatal false
+end
+
+require "extend/os/requirements/non_binary_osxfuse_requirement"
diff --git a/Library/Homebrew/requirements/osxfuse_requirement.rb b/Library/Homebrew/requirements/osxfuse_requirement.rb
index 9a07209d43..2e67a4b050 100644
--- a/Library/Homebrew/requirements/osxfuse_requirement.rb
+++ b/Library/Homebrew/requirements/osxfuse_requirement.rb
@@ -1,11 +1,8 @@
 require "requirement"
 
 class OsxfuseRequirement < Requirement
+  cask "osxfuse"
   fatal true
 end
 
-class NonBinaryOsxfuseRequirement < Requirement
-  fatal false
-end
-
 require "extend/os/requirements/osxfuse_requirement"
diff --git a/Library/Homebrew/requirements/x11_requirement.rb b/Library/Homebrew/requirements/x11_requirement.rb
index 65ce6396fb..6ffcc2db71 100644
--- a/Library/Homebrew/requirements/x11_requirement.rb
+++ b/Library/Homebrew/requirements/x11_requirement.rb
@@ -5,6 +5,9 @@ class X11Requirement < Requirement
 
   fatal true
 
+  cask "xquartz"
+  download "https://xquartz.macosforge.org"
+
   env { ENV.x11 }
 
   def initialize(name = "x11", tags = [])
diff --git a/Library/Homebrew/rubocops/components_order_cop.rb b/Library/Homebrew/rubocops/components_order_cop.rb
index a1a576177b..912f4d3804 100644
--- a/Library/Homebrew/rubocops/components_order_cop.rb
+++ b/Library/Homebrew/rubocops/components_order_cop.rb
@@ -2,7 +2,7 @@ require_relative "./extend/formula_cop"
 
 module RuboCop
   module Cop
-    module FormulaAuditStrict
+    module FormulaAudit
       # This cop checks for correct order of components in a Formula
       #
       # - component_precedence_list has component hierarchy in a nested list
@@ -62,8 +62,14 @@ module RuboCop
           end
         end
 
+        # `aspell`: options and resources should be grouped by language
+        WHITELIST = %w[
+          aspell
+        ].freeze
+
         # Method to format message for reporting component precedence violations
         def component_problem(c1, c2)
+          return if WHITELIST.include?(@formula_name)
           problem "`#{format_component(c1)}` (line #{line_number(c1)}) should be put before `#{format_component(c2)}` (line #{line_number(c2)})"
         end
 
diff --git a/Library/Homebrew/rubocops/components_redundancy_cop.rb b/Library/Homebrew/rubocops/components_redundancy_cop.rb
index 7495b986b7..e22ec6a910 100644
--- a/Library/Homebrew/rubocops/components_redundancy_cop.rb
+++ b/Library/Homebrew/rubocops/components_redundancy_cop.rb
@@ -2,7 +2,7 @@ require_relative "./extend/formula_cop"
 
 module RuboCop
   module Cop
-    module FormulaAuditStrict
+    module FormulaAudit
       # This cop checks if redundant components are present and other component errors
       #
       # - `url|checksum|mirror` should be inside `stable` block
diff --git a/Library/Homebrew/rubocops/extend/formula_cop.rb b/Library/Homebrew/rubocops/extend/formula_cop.rb
index ae343a9fc2..55f22bbc61 100644
--- a/Library/Homebrew/rubocops/extend/formula_cop.rb
+++ b/Library/Homebrew/rubocops/extend/formula_cop.rb
@@ -99,6 +99,17 @@ module RuboCop
         end
       end
 
+      # Returns array of function call nodes matching func_name in every descendant of node
+      #           Ex. function call:  foo(*args, **kwargs)
+      # Does not match method calls:  foo.bar(*args, **kwargs)
+      # Returns every function calls if no func_name is passed
+      def find_every_func_call_by_name(node, func_name = nil)
+        return if node.nil?
+        node.each_descendant(:send).select do |func_node|
+          func_node.receiver.nil? && (func_name.nil? || func_name == func_node.method_name)
+        end
+      end
+
       # Given a method_name and arguments, yields to a block with
       # matching method passed as a parameter to the block
       def find_method_with_args(node, method_name, *args)
diff --git a/Library/Homebrew/rubocops/urls_cop.rb b/Library/Homebrew/rubocops/urls_cop.rb
index 4ef801689d..30420a793a 100644
--- a/Library/Homebrew/rubocops/urls_cop.rb
+++ b/Library/Homebrew/rubocops/urls_cop.rb
@@ -6,8 +6,8 @@ module RuboCop
       # This cop audits urls and mirrors in Formulae
       class Urls < FormulaCop
         def audit_formula(_node, _class_node, _parent_class_node, body_node)
-          urls = find_every_method_call_by_name(body_node, :url)
-          mirrors = find_every_method_call_by_name(body_node, :mirror)
+          urls = find_every_func_call_by_name(body_node, :url)
+          mirrors = find_every_func_call_by_name(body_node, :mirror)
 
           # GNU urls; doesn't apply to mirrors
           gnu_pattern = %r{^(?:https?|ftp)://ftpmirror.gnu.org/(.*)}
@@ -191,12 +191,11 @@ module RuboCop
           end
         end
       end
-    end
-    module FormulaAuditStrict
+
       class PyPiUrls < FormulaCop
         def audit_formula(_node, _class_node, _parent_class_node, body_node)
-          urls = find_every_method_call_by_name(body_node, :url)
-          mirrors = find_every_method_call_by_name(body_node, :mirror)
+          urls = find_every_func_call_by_name(body_node, :url)
+          mirrors = find_every_func_call_by_name(body_node, :mirror)
           urls += mirrors
 
           # Check pypi urls
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index df7b86770c..ce3cac8064 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -42,6 +42,7 @@ class SoftwareSpec
     @deprecated_options = []
     @build = BuildOptions.new(Options.create(@flags), options)
     @compiler_failures = []
+    @bottle_disable_reason = nil
   end
 
   def owner=(owner)
@@ -127,9 +128,9 @@ class SoftwareSpec
   def option(name, description = "")
     opt = PREDEFINED_OPTIONS.fetch(name) do
       if name.is_a?(Symbol)
-        odeprecated "passing arbitrary symbols (i.e. #{name.inspect}) to `option`"
-        name = name.to_s
+        odisabled "passing arbitrary symbols (i.e. #{name.inspect}) to `option`"
       end
+
       unless name.is_a?(String)
         raise ArgumentError, "option name must be string or symbol; got a #{name.class}: #{name}"
       end
@@ -204,7 +205,7 @@ class SoftwareSpec
   end
 
   def fails_with(compiler, &block)
-    odeprecated "fails_with :llvm" if compiler == :llvm
+    odisabled "fails_with :llvm" if compiler == :llvm
     compiler_failures << CompilerFailure.create(compiler, &block)
   end
 
diff --git a/Library/Homebrew/system_config.rb b/Library/Homebrew/system_config.rb
index 13867e7d4e..f42572add0 100644
--- a/Library/Homebrew/system_config.rb
+++ b/Library/Homebrew/system_config.rb
@@ -1,27 +1,10 @@
 require "hardware"
 require "software_spec"
 require "rexml/document"
-require "tap"
 require "development_tools"
 
 class SystemConfig
   class << self
-    def gcc_4_2
-      @gcc_4_2 ||= if DevelopmentTools.installed?
-        DevelopmentTools.gcc_4_2_build_version
-      else
-        Version::NULL
-      end
-    end
-
-    def gcc_4_0
-      @gcc_4_0 ||= if DevelopmentTools.installed?
-        DevelopmentTools.gcc_4_0_build_version
-      else
-        Version::NULL
-      end
-    end
-
     def clang
       @clang ||= if DevelopmentTools.installed?
         DevelopmentTools.clang_version
@@ -72,42 +55,6 @@ class SystemConfig
       end
     end
 
-    def describe_perl
-      describe_path(which("perl", ENV["HOMEBREW_PATH"]))
-    end
-
-    def describe_python
-      python = begin
-        python_path = PATH.new(ENV["HOMEBREW_PATH"])
-                          .prepend(Formula["python"].opt_libexec/"bin")
-        which "python", python_path
-      rescue FormulaUnavailableError
-        which "python"
-      end
-
-      return "N/A" if python.nil?
-      python_binary = Utils.popen_read python, "-c", "import sys; sys.stdout.write(sys.executable)"
-      python_binary = Pathname.new(python_binary).realpath
-      if python == python_binary
-        python
-      else
-        "#{python} => #{python_binary}"
-      end
-    end
-
-    def describe_ruby
-      ruby = which "ruby", ENV["HOMEBREW_PATH"]
-      return "N/A" if ruby.nil?
-      ruby_binary = Utils.popen_read ruby, "-rrbconfig", "-e", \
-        'include RbConfig;print"#{CONFIG["bindir"]}/#{CONFIG["ruby_install_name"]}#{CONFIG["EXEEXT"]}"'
-      ruby_binary = Pathname.new(ruby_binary).realpath
-      if ruby == ruby_binary
-        ruby
-      else
-        "#{ruby} => #{ruby_binary}"
-      end
-    end
-
     def describe_homebrew_ruby_version
       case RUBY_VERSION
       when /^1\.[89]/, /^2\.0/
@@ -168,6 +115,7 @@ class SystemConfig
         HOMEBREW_REPOSITORY: "/usr/local/Homebrew",
         HOMEBREW_CELLAR: "/usr/local/Cellar",
         HOMEBREW_CACHE: "#{ENV["HOME"]}/Library/Caches/Homebrew",
+        HOMEBREW_RUBY_WARNINGS: "-W0",
       }.freeze
       boring_keys = %w[
         HOMEBREW_BROWSER
@@ -183,7 +131,6 @@ class SystemConfig
         HOMEBREW_LIBRARY
         HOMEBREW_MACOS_VERSION
         HOMEBREW_RUBY_PATH
-        HOMEBREW_RUBY_WARNINGS
         HOMEBREW_SYSTEM
         HOMEBREW_OS_VERSION
         HOMEBREW_PATH
@@ -203,17 +150,20 @@ class SystemConfig
       if defaults_hash[:HOMEBREW_CACHE] != HOMEBREW_CACHE.to_s
         f.puts "HOMEBREW_CACHE: #{HOMEBREW_CACHE}"
       end
-      ENV.sort.each do |key, value|
-        next unless key.start_with?("HOMEBREW_")
-        next if boring_keys.include?(key)
-        next if defaults_hash[key.to_sym]
-        value = "set" if key =~ /(cookie|key|token|password)/i
-        f.puts "#{key}: #{value}"
+      if defaults_hash[:HOMEBREW_RUBY_WARNINGS] != ENV["HOMEBREW_RUBY_WARNINGS"].to_s
+        f.puts "HOMEBREW_RUBY_WARNINGS: #{ENV["HOMEBREW_RUBY_WARNINGS"]}"
+      end
+      unless ENV["HOMEBREW_ENV"]
+        ENV.sort.each do |key, value|
+          next unless key.start_with?("HOMEBREW_")
+          next if boring_keys.include?(key)
+          next if defaults_hash[key.to_sym]
+          value = "set" if key =~ /(cookie|key|token|password)/i
+          f.puts "#{key}: #{value}"
+        end
       end
       f.puts hardware if hardware
       f.puts "Homebrew Ruby: #{describe_homebrew_ruby}"
-      f.puts "GCC-4.0: build #{gcc_4_0}" unless gcc_4_0.null?
-      f.puts "GCC-4.2: build #{gcc_4_2}" unless gcc_4_2.null?
       f.print "Clang: "
       if clang.null?
         f.puts "N/A"
@@ -227,9 +177,6 @@ class SystemConfig
       end
       f.puts "Git: #{describe_git}"
       f.puts "Curl: #{describe_curl}"
-      f.puts "Perl: #{describe_perl}"
-      f.puts "Python: #{describe_python}"
-      f.puts "Ruby: #{describe_ruby}"
       f.puts "Java: #{describe_java}"
     end
     alias dump_generic_verbose_config dump_verbose_config
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index e13b9af754..bcd205bab8 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -1,4 +1,3 @@
-require "extend/string"
 require "extend/cachable"
 require "readall"
 
@@ -78,6 +77,8 @@ class Tap
     @full_name = "#{@user}/homebrew-#{@repo}"
     @path = TAP_DIRECTORY/@full_name.downcase
     @path.extend(GitRepositoryExtension)
+    @alias_table = nil
+    @alias_reverse_table = nil
   end
 
   # clear internal cache
@@ -200,7 +201,9 @@ class Tap
   # install this {Tap}.
   #
   # @param [Hash] options
-  # @option options [String]  :clone_targe If passed, it will be used as the clone remote.
+  # @option options [String] :clone_target If passed, it will be used as the clone remote.
+  # @option options [Boolean, nil] :force_auto_update If present, whether to override the
+  #   logic that skips non-GitHub repositories during auto-updates.
   # @option options [Boolean] :full_clone If set as true, full clone will be used.
   # @option options [Boolean] :quiet If set, suppress all output.
   def install(options = {})
@@ -209,12 +212,14 @@ class Tap
     full_clone = options.fetch(:full_clone, false)
     quiet = options.fetch(:quiet, false)
     requested_remote = options[:clone_target] || default_remote
+    # if :force_auto_update is unset, use nil, meaning "no change"
+    force_auto_update = options.fetch(:force_auto_update, nil)
 
     if official? && DEPRECATED_OFFICIAL_TAPS.include?(repo)
       odie "#{name} was deprecated. This tap is now empty as all its formulae were migrated."
     end
 
-    if installed?
+    if installed? && force_auto_update.nil?
       raise TapAlreadyTappedError, name unless full_clone
       raise TapAlreadyUnshallowError, name unless shallow?
     end
@@ -223,6 +228,11 @@ class Tap
     Utils.ensure_git_installed!
 
     if installed?
+      unless force_auto_update.nil?
+        config["forceautoupdate"] = force_auto_update
+        return if !full_clone || !shallow?
+      end
+
       if options[:clone_target] && requested_remote != remote
         raise TapRemoteMismatchError.new(name, @remote, requested_remote)
       end
@@ -258,6 +268,8 @@ class Tap
       raise
     end
 
+    config["forceautoupdate"] = force_auto_update unless force_auto_update.nil?
+
     link_completions_and_manpages
 
     formula_count = formula_files.size
diff --git a/Library/Homebrew/test/Gemfile.lock b/Library/Homebrew/test/Gemfile.lock
index b69a5f0a71..f5b13e4fbf 100644
--- a/Library/Homebrew/test/Gemfile.lock
+++ b/Library/Homebrew/test/Gemfile.lock
@@ -12,7 +12,7 @@ GEM
     parallel (1.12.1)
     parallel_tests (2.21.2)
       parallel
-    parser (2.5.0.2)
+    parser (2.5.0.5)
       ast (~> 2.4.0)
     powerpack (0.1.1)
     rainbow (3.0.0)
@@ -36,7 +36,7 @@ GEM
     rspec-support (3.7.1)
     rspec-wait (0.0.9)
       rspec (>= 3, < 4)
-    rubocop (0.53.0)
+    rubocop (0.55.0)
       parallel (~> 1.10)
       parser (>= 2.5)
       powerpack (~> 0.1)
@@ -62,7 +62,7 @@ DEPENDENCIES
   rspec-its
   rspec-retry
   rspec-wait
-  rubocop (= 0.53.0)
+  rubocop (= 0.55.0)
   simplecov
 
 BUNDLED WITH
diff --git a/Library/Homebrew/test/PATH_spec.rb b/Library/Homebrew/test/PATH_spec.rb
index 68233c23c7..b6f884d665 100644
--- a/Library/Homebrew/test/PATH_spec.rb
+++ b/Library/Homebrew/test/PATH_spec.rb
@@ -23,6 +23,13 @@ describe PATH do
     it "returns a PATH array" do
       expect(described_class.new("/path1", "/path2").to_ary).to eq(["/path1", "/path2"])
     end
+
+    it "does not allow mutating the original" do
+      path = described_class.new("/path1", "/path2")
+      path.to_ary << "/path3"
+
+      expect(path).not_to include("/path3")
+    end
   end
 
   describe "#to_str" do
@@ -61,6 +68,12 @@ describe PATH do
     end
   end
 
+  describe "#==" do
+    it "always returns false when comparing against something which does not respons to `#to_ary` or `#to_str`" do
+      expect(described_class.new).not_to eq Object.new
+    end
+  end
+
   describe "#include?" do
     it "returns true if a path is included" do
       path = described_class.new("/path1", "/path2")
diff --git a/Library/Homebrew/test/cask/artifact/generic_artifact_spec.rb b/Library/Homebrew/test/cask/artifact/generic_artifact_spec.rb
index 7e12854760..5502d83ed7 100644
--- a/Library/Homebrew/test/cask/artifact/generic_artifact_spec.rb
+++ b/Library/Homebrew/test/cask/artifact/generic_artifact_spec.rb
@@ -19,7 +19,7 @@ describe Hbc::Artifact::Artifact, :cask do
   context "without target" do
     it "fails to load" do
       expect {
-        Hbc::CaskLoader.load(cask_path("with-generic-artifact-no-target"))
+        Hbc::CaskLoader.load(cask_path("invalid/invalid-generic-artifact-no-target"))
       }.to raise_error(Hbc::CaskInvalidError, /target required for Generic Artifact/)
     end
   end
diff --git a/Library/Homebrew/test/cask/artifact/two_apps_incorrect_spec.rb b/Library/Homebrew/test/cask/artifact/two_apps_incorrect_spec.rb
deleted file mode 100644
index cda5b4488c..0000000000
--- a/Library/Homebrew/test/cask/artifact/two_apps_incorrect_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-describe Hbc::Artifact::App, :cask do
-  # FIXME: Doesn't actually raise because the `app` stanza is not evaluated on load.
-  # it "must raise" do
-  #   lambda {
-  #     Hbc::CaskLoader.load(cask_path("with-two-apps-incorrect"))
-  #   }.must_raise
-  #   # TODO: later give the user a nice exception for this case and check for it here
-  # end
-end
diff --git a/Library/Homebrew/test/cask/cask_spec.rb b/Library/Homebrew/test/cask/cask_spec.rb
index e8d5aff8f8..4b9393d6cc 100644
--- a/Library/Homebrew/test/cask/cask_spec.rb
+++ b/Library/Homebrew/test/cask/cask_spec.rb
@@ -70,14 +70,6 @@ describe Hbc::Cask, :cask do
     end
   end
 
-  describe "all_tokens" do
-    it "returns a token for every Cask" do
-      all_cask_tokens = Hbc.all_tokens
-      expect(all_cask_tokens.count).to be > 20
-      all_cask_tokens.each { |token| expect(token).to be_kind_of(String) }
-    end
-  end
-
   describe "metadata" do
     it "proposes a versioned metadata directory name for each instance" do
       cask_token = "local-caffeine"
diff --git a/Library/Homebrew/test/cask/cli/audit_spec.rb b/Library/Homebrew/test/cask/cli/audit_spec.rb
index da8bf12737..2ed4ea9f11 100644
--- a/Library/Homebrew/test/cask/cli/audit_spec.rb
+++ b/Library/Homebrew/test/cask/cli/audit_spec.rb
@@ -7,9 +7,7 @@ describe Hbc::CLI::Audit, :cask do
 
   describe "selection of Casks to audit" do
     it "audits all Casks if no tokens are given" do
-      expect(cask).to be_a Hbc::Cask
-
-      allow(Hbc).to receive(:all).and_return([cask, cask])
+      allow(Hbc::Cask).to receive(:to_a).and_return([cask, cask])
 
       expect(Hbc::Auditor).to receive(:audit).twice.and_return(true)
 
diff --git a/Library/Homebrew/test/cask/cli/style_spec.rb b/Library/Homebrew/test/cask/cli/style_spec.rb
index aaf3248f17..6f486ea939 100644
--- a/Library/Homebrew/test/cask/cli/style_spec.rb
+++ b/Library/Homebrew/test/cask/cli/style_spec.rb
@@ -83,11 +83,13 @@ describe Hbc::CLI::Style, :cask do
     context "when no cask tokens are given" do
       let(:tokens) { [] }
 
-      before do
-        allow(Hbc).to receive(:all_tapped_cask_dirs).and_return(%w[Casks MoreCasks])
+      matcher :a_path_ending_with do |end_string|
+        match do |actual|
+          expect(actual.to_s).to end_with(end_string)
+        end
       end
 
-      it { is_expected.to eq(%w[Casks MoreCasks]) }
+      it { is_expected.to contain_exactly(a_path_ending_with("/caskroom/homebrew-spec/Casks"), a_path_ending_with("/third-party/homebrew-tap/Casks")) }
     end
 
     context "when at least one cask token is a path that exists" do
diff --git a/Library/Homebrew/test/cask/dsl_spec.rb b/Library/Homebrew/test/cask/dsl_spec.rb
index 3e16b915ea..0348daab13 100644
--- a/Library/Homebrew/test/cask/dsl_spec.rb
+++ b/Library/Homebrew/test/cask/dsl_spec.rb
@@ -72,7 +72,7 @@ describe Hbc::DSL, :cask do
     end
 
     context "when it contains a deprecated DSL version", :needs_compat do
-      let(:token) { "with-dsl-version" }
+      let(:token) { "compat/with-dsl-version" }
 
       it "may use deprecated DSL version hash syntax" do
         allow(ENV).to receive(:[]).with("HOMEBREW_DEVELOPER").and_return(nil)
diff --git a/Library/Homebrew/test/cask/scopes_spec.rb b/Library/Homebrew/test/cask/scopes_spec.rb
deleted file mode 100644
index d1c03b9b0c..0000000000
--- a/Library/Homebrew/test/cask/scopes_spec.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-describe Hbc::Scopes, :cask do
-  describe "installed" do
-    it "returns a list installed Casks by loading Casks for all the dirs that exist in the caskroom" do
-      allow(Hbc::CaskLoader).to receive(:load) { |token| "loaded-#{token}" }
-
-      Hbc.caskroom.join("cask-bar").mkpath
-      Hbc.caskroom.join("cask-foo").mkpath
-
-      installed_casks = Hbc.installed
-
-      expect(Hbc::CaskLoader).to have_received(:load).with("cask-bar")
-      expect(Hbc::CaskLoader).to have_received(:load).with("cask-foo")
-      expect(installed_casks).to eq(
-        %w[
-          loaded-cask-bar
-          loaded-cask-foo
-        ],
-      )
-    end
-
-    it "optimizes performance by resolving to a fully qualified path before calling Hbc::CaskLoader.load" do
-      fake_tapped_cask_dir = Pathname.new(Dir.mktmpdir).join("Casks")
-      absolute_path_to_cask = fake_tapped_cask_dir.join("some-cask.rb")
-
-      allow(Hbc::CaskLoader).to receive(:load)
-      allow(Hbc).to receive(:all_tapped_cask_dirs) { [fake_tapped_cask_dir] }
-
-      Hbc.caskroom.join("some-cask").mkdir
-      fake_tapped_cask_dir.mkdir
-      FileUtils.touch(absolute_path_to_cask)
-
-      Hbc.installed
-
-      expect(Hbc::CaskLoader).to have_received(:load).with(absolute_path_to_cask)
-    end
-  end
-end
diff --git a/Library/Homebrew/test/cleanup_spec.rb b/Library/Homebrew/test/cleanup_spec.rb
index 9ec3a30479..40ab4280b7 100644
--- a/Library/Homebrew/test/cleanup_spec.rb
+++ b/Library/Homebrew/test/cleanup_spec.rb
@@ -1,7 +1,6 @@
 require "test/support/fixtures/testball"
 require "cleanup"
 require "fileutils"
-require "pathname"
 
 describe Homebrew::Cleanup do
   let(:ds_store) { Pathname.new("#{HOMEBREW_PREFIX}/Library/.DS_Store") }
diff --git a/Library/Homebrew/test/cli_parser_spec.rb b/Library/Homebrew/test/cli_parser_spec.rb
index 037f007a27..5f65a80c15 100644
--- a/Library/Homebrew/test/cli_parser_spec.rb
+++ b/Library/Homebrew/test/cli_parser_spec.rb
@@ -16,24 +16,25 @@ describe Homebrew::CLI::Parser do
     }
 
     it "parses short option" do
-      args = parser.parse(["-v"])
-      expect(args).to be_verbose
+      parser.parse(["-v"])
+      expect(Homebrew.args).to be_verbose
     end
 
     it "parses a single valid option" do
-      args = parser.parse(["--verbose"])
-      expect(args).to be_verbose
+      parser.parse(["--verbose"])
+      expect(Homebrew.args).to be_verbose
     end
 
     it "parses a valid option along with few unnamed args" do
       args = %w[--verbose unnamed args]
       parser.parse(args)
-      expect(args).to eq %w[unnamed args]
+      expect(Homebrew.args).to be_verbose
+      expect(args).to eq %w[--verbose unnamed args]
     end
 
     it "parses a single option and checks other options to be nil" do
       args = parser.parse(["--verbose"])
-      expect(args).to be_verbose
+      expect(Homebrew.args).to be_verbose
       expect(args.more_verbose?).to be nil
     end
 
@@ -50,8 +51,8 @@ describe Homebrew::CLI::Parser do
   describe "test long flag options" do
     subject(:parser) {
       described_class.new do
-        flag        "--filename", description: "Name of the file", required: true
-        comma_array "--files",    description: "Comma separated filenames"
+        flag        "--filename=", description: "Name of the file"
+        comma_array "--files",     description: "Comma separated filenames"
       end
     }
 
@@ -60,7 +61,7 @@ describe Homebrew::CLI::Parser do
       expect(args.filename).to eq "random.txt"
     end
 
-    it "raises an exception when a flag's required arg is not passed" do
+    it "raises an exception when a flag's required value is not passed" do
       expect { parser.parse(["--filename"]) }.to raise_error(OptionParser::MissingArgument, /--filename/)
     end
 
diff --git a/Library/Homebrew/test/cmd/linkapps_spec.rb b/Library/Homebrew/test/cmd/linkapps_spec.rb
deleted file mode 100644
index 8fc0d5eb91..0000000000
--- a/Library/Homebrew/test/cmd/linkapps_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-describe "brew linkapps", :integration_test do
-  let(:home_dir) { mktmpdir }
-  let(:apps_dir) { home_dir/"Applications" }
-
-  it "symlinks applications" do
-    apps_dir.mkpath
-
-    setup_test_formula "testball"
-
-    source_app = HOMEBREW_CELLAR/"testball/0.1/TestBall.app"
-    source_app.mkpath
-
-    ENV.delete "HOMEBREW_DEVELOPER"
-
-    expect { brew "linkapps", "--local", "HOME" => home_dir }
-      .to output(/Linking: #{Regexp.escape(source_app)}/).to_stdout
-      .and output(/'brew linkapps' is deprecated/).to_stderr
-      .and be_a_success
-
-    expect(apps_dir/"TestBall.app").to be_a_symlink
-  end
-end
diff --git a/Library/Homebrew/test/cmd/missing_spec.rb b/Library/Homebrew/test/cmd/missing_spec.rb
index f84dd66567..4c1b4367a8 100644
--- a/Library/Homebrew/test/cmd/missing_spec.rb
+++ b/Library/Homebrew/test/cmd/missing_spec.rb
@@ -14,7 +14,7 @@ describe "brew missing", :integration_test do
     expect { brew "missing" }
       .to output("foo\n").to_stdout
       .and not_to_output.to_stderr
-      .and be_a_success
+      .and be_a_failure
   end
 
   it "prints nothing if all dependencies are installed" do
@@ -35,7 +35,7 @@ describe "brew missing", :integration_test do
       expect { brew "missing", "--hide=foo" }
         .to output("bar: foo\n").to_stdout
         .and not_to_output.to_stderr
-        .and be_a_success
+        .and be_a_failure
     end
   end
 end
diff --git a/Library/Homebrew/test/cmd/search_spec.rb b/Library/Homebrew/test/cmd/search_spec.rb
index c55a51e4fe..15c66cba31 100644
--- a/Library/Homebrew/test/cmd/search_spec.rb
+++ b/Library/Homebrew/test/cmd/search_spec.rb
@@ -1,7 +1,6 @@
 describe "brew search", :integration_test do
   before do
     setup_test_formula "testball"
-    setup_remote_tap "caskroom/cask"
   end
 
   it "lists all available Formulae when no argument is given" do
@@ -26,6 +25,8 @@ describe "brew search", :integration_test do
   end
 
   it "falls back to a GitHub tap search when no formula is found", :needs_network, retry: 3 do
+    setup_remote_tap "caskroom/cask"
+
     expect { brew "search", "caskroom/cask/firefox" }
       .to output(/firefox/).to_stdout
       .and output(/Searching/).to_stderr
diff --git a/Library/Homebrew/test/cmd/switch_spec.rb b/Library/Homebrew/test/cmd/switch_spec.rb
index 48d7dcdd08..fbf44810b9 100644
--- a/Library/Homebrew/test/cmd/switch_spec.rb
+++ b/Library/Homebrew/test/cmd/switch_spec.rb
@@ -1,7 +1,7 @@
 describe "brew switch", :integration_test do
   it "allows switching between Formula versions" do
     expect { brew "switch" }
-      .to output(/Usage: brew switch <name> <version>/).to_stderr
+      .to output(/Usage: brew switch <formula> <version>/).to_stderr
       .and not_to_output.to_stdout
       .and be_a_failure
 
@@ -25,7 +25,7 @@ describe "brew switch", :integration_test do
       .and be_a_success
 
     expect { brew "switch", "testball", "0.3" }
-      .to output("Versions available: 0.1, 0.2\n").to_stdout
+      .to output("testball installed versions: 0.1, 0.2\n").to_stdout
       .and output(/testball does not have a version "0.3"/).to_stderr
       .and be_a_failure
   end
diff --git a/Library/Homebrew/test/cmd/unlinkapps_spec.rb b/Library/Homebrew/test/cmd/unlinkapps_spec.rb
deleted file mode 100644
index 397a8ec5e2..0000000000
--- a/Library/Homebrew/test/cmd/unlinkapps_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-describe "brew unlinkapps", :integration_test do
-  let(:home_dir) { mktmpdir }
-  let(:apps_dir) { home_dir/"Applications" }
-
-  it "unlinks symlinked applications" do
-    apps_dir.mkpath
-
-    setup_test_formula "testball"
-
-    source_app = HOMEBREW_CELLAR/"testball/0.1/TestBall.app"
-    source_app.mkpath
-
-    FileUtils.ln_s source_app, apps_dir/"TestBall.app"
-
-    ENV.delete "HOMEBREW_DEVELOPER"
-
-    expect { brew "unlinkapps", "--local", "HOME" => home_dir }
-      .to output(%r{Unlinking: #{Regexp.escape(apps_dir)}/TestBall.app}).to_stdout
-      .and output(/'brew unlinkapps' is deprecated/).to_stderr
-      .and be_a_success
-  end
-end
diff --git a/Library/Homebrew/test/dev-cmd/audit_spec.rb b/Library/Homebrew/test/dev-cmd/audit_spec.rb
index c9264f22b5..83b3ad215a 100644
--- a/Library/Homebrew/test/dev-cmd/audit_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/audit_spec.rb
@@ -8,596 +8,598 @@ module Count
   end
 end
 
-describe FormulaText do
-  alias_matcher :have_data, :be_data
-  alias_matcher :have_end, :be_end
-  alias_matcher :have_trailing_newline, :be_trailing_newline
+module Homebrew
+  describe FormulaText do
+    alias_matcher :have_data, :be_data
+    alias_matcher :have_end, :be_end
+    alias_matcher :have_trailing_newline, :be_trailing_newline
 
-  let(:dir) { mktmpdir }
+    let(:dir) { mktmpdir }
 
-  def formula_text(name, body = nil, options = {})
-    path = dir/"#{name}.rb"
+    def formula_text(name, body = nil, options = {})
+      path = dir/"#{name}.rb"
 
-    path.write <<~EOS
-      class #{Formulary.class_s(name)} < Formula
-        #{body}
+      path.write <<~EOS
+        class #{Formulary.class_s(name)} < Formula
+          #{body}
+        end
+        #{options[:patch]}
+      EOS
+
+      described_class.new(path)
+    end
+
+    specify "simple valid Formula" do
+      ft = formula_text "valid", <<~EOS
+        url "http://www.example.com/valid-1.0.tar.gz"
+      EOS
+
+      expect(ft).not_to have_data
+      expect(ft).not_to have_end
+      expect(ft).to have_trailing_newline
+
+      expect(ft =~ /\burl\b/).to be_truthy
+      expect(ft.line_number(/desc/)).to be nil
+      expect(ft.line_number(/\burl\b/)).to eq(2)
+      expect(ft).to include("Valid")
+    end
+
+    specify "#trailing_newline?" do
+      ft = formula_text "newline"
+      expect(ft).to have_trailing_newline
+    end
+
+    specify "#data?" do
+      ft = formula_text "data", <<~EOS
+        patch :DATA
+      EOS
+
+      expect(ft).to have_data
+    end
+
+    specify "#end?" do
+      ft = formula_text "end", "", patch: "__END__\na patch here"
+      expect(ft).to have_end
+      expect(ft.without_patch).to eq("class End < Formula\n  \nend")
+    end
+  end
+
+  describe FormulaAuditor do
+    def formula_auditor(name, text, options = {})
+      path = Pathname.new "#{dir}/#{name}.rb"
+      path.open("w") do |f|
+        f.write text
       end
-      #{options[:patch]}
-    EOS
 
-    described_class.new(path)
-  end
-
-  specify "simple valid Formula" do
-    ft = formula_text "valid", <<~EOS
-      url "http://www.example.com/valid-1.0.tar.gz"
-    EOS
-
-    expect(ft).not_to have_data
-    expect(ft).not_to have_end
-    expect(ft).to have_trailing_newline
-
-    expect(ft =~ /\burl\b/).to be_truthy
-    expect(ft.line_number(/desc/)).to be nil
-    expect(ft.line_number(/\burl\b/)).to eq(2)
-    expect(ft).to include("Valid")
-  end
-
-  specify "#trailing_newline?" do
-    ft = formula_text "newline"
-    expect(ft).to have_trailing_newline
-  end
-
-  specify "#data?" do
-    ft = formula_text "data", <<~EOS
-      patch :DATA
-    EOS
-
-    expect(ft).to have_data
-  end
-
-  specify "#end?" do
-    ft = formula_text "end", "", patch: "__END__\na patch here"
-    expect(ft).to have_end
-    expect(ft.without_patch).to eq("class End < Formula\n  \nend")
-  end
-end
-
-describe FormulaAuditor do
-  def formula_auditor(name, text, options = {})
-    path = Pathname.new "#{dir}/#{name}.rb"
-    path.open("w") do |f|
-      f.write text
+      described_class.new(Formulary.factory(path), options)
     end
 
-    described_class.new(Formulary.factory(path), options)
-  end
+    let(:dir) { mktmpdir }
 
-  let(:dir) { mktmpdir }
+    describe "#problems" do
+      it "is empty by default" do
+        fa = formula_auditor "foo", <<~EOS
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+          end
+        EOS
 
-  describe "#problems" do
-    it "is empty by default" do
-      fa = formula_auditor "foo", <<~EOS
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-        end
-      EOS
-
-      expect(fa.problems).to be_empty
-    end
-  end
-
-  describe "#audit_file" do
-    specify "file permissions" do
-      allow(File).to receive(:umask).and_return(022)
-
-      fa = formula_auditor "foo", <<~EOS
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-        end
-      EOS
-
-      path = fa.formula.path
-      path.chmod 0400
-
-      fa.audit_file
-      expect(fa.problems)
-        .to eq(["Incorrect file permissions (400): chmod 644 #{path}"])
+        expect(fa.problems).to be_empty
+      end
     end
 
-    specify "DATA but no __END__" do
-      fa = formula_auditor "foo", <<~EOS
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-          patch :DATA
-        end
-      EOS
+    describe "#audit_file" do
+      specify "file permissions" do
+        allow(File).to receive(:umask).and_return(022)
 
-      fa.audit_file
-      expect(fa.problems).to eq(["'DATA' was found, but no '__END__'"])
+        fa = formula_auditor "foo", <<~EOS
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+          end
+        EOS
+
+        path = fa.formula.path
+        path.chmod 0400
+
+        fa.audit_file
+        expect(fa.problems)
+          .to eq(["Incorrect file permissions (400): chmod 644 #{path}"])
+      end
+
+      specify "DATA but no __END__" do
+        fa = formula_auditor "foo", <<~EOS
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+            patch :DATA
+          end
+        EOS
+
+        fa.audit_file
+        expect(fa.problems).to eq(["'DATA' was found, but no '__END__'"])
+      end
+
+      specify "__END__ but no DATA" do
+        fa = formula_auditor "foo", <<~EOS
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+          end
+          __END__
+          a patch goes here
+        EOS
+
+        fa.audit_file
+        expect(fa.problems).to eq(["'__END__' was found, but 'DATA' is not used"])
+      end
+
+      specify "no trailing newline" do
+        fa = formula_auditor "foo", 'class Foo<Formula; url "file:///foo-1.0.tgz";end'
+
+        fa.audit_file
+        expect(fa.problems).to eq(["File should end with a newline"])
+      end
+
+      specify "no issue" do
+        fa = formula_auditor "foo", <<~EOS
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+            homepage "http://example.com"
+          end
+        EOS
+
+        fa.audit_file
+        expect(fa.problems).to eq([])
+      end
     end
 
-    specify "__END__ but no DATA" do
-      fa = formula_auditor "foo", <<~EOS
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-        end
-        __END__
-        a patch goes here
-      EOS
+    describe "#line_problems" do
+      specify "pkgshare" do
+        fa = formula_auditor "foo", <<~EOS, strict: true
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+          end
+        EOS
 
-      fa.audit_file
-      expect(fa.problems).to eq(["'__END__' was found, but 'DATA' is not used"])
+        fa.line_problems 'ohai "#{share}/foo"', 3
+        expect(fa.problems.shift).to eq("Use \#{pkgshare} instead of \#{share}/foo")
+
+        fa.line_problems 'ohai "#{share}/foo/bar"', 3
+        expect(fa.problems.shift).to eq("Use \#{pkgshare} instead of \#{share}/foo")
+
+        fa.line_problems 'ohai share/"foo"', 3
+        expect(fa.problems.shift).to eq('Use pkgshare instead of (share/"foo")')
+
+        fa.line_problems 'ohai share/"foo/bar"', 3
+        expect(fa.problems.shift).to eq('Use pkgshare instead of (share/"foo")')
+
+        fa.line_problems 'ohai "#{share}/foo-bar"', 3
+        expect(fa.problems).to eq([])
+
+        fa.line_problems 'ohai share/"foo-bar"', 3
+        expect(fa.problems).to eq([])
+
+        fa.line_problems 'ohai share/"bar"', 3
+        expect(fa.problems).to eq([])
+      end
+
+      # Regression test for https://github.com/Homebrew/legacy-homebrew/pull/48744
+      # Formulae with "++" in their name would break various audit regexps:
+      #   Error: nested *?+ in regexp: /^libxml++3\s/
+      specify "++ in name" do
+        fa = formula_auditor "foolibc++", <<~EOS, strict: true
+          class Foolibcxx < Formula
+            desc "foolibc++ is a test"
+            url "http://example.com/foo-1.0.tgz"
+          end
+        EOS
+
+        fa.line_problems 'ohai "#{share}/foolibc++"', 3
+        expect(fa.problems.shift)
+          .to eq("Use \#{pkgshare} instead of \#{share}/foolibc++")
+
+        fa.line_problems 'ohai share/"foolibc++"', 3
+        expect(fa.problems.shift)
+          .to eq('Use pkgshare instead of (share/"foolibc++")')
+      end
     end
 
-    specify "no trailing newline" do
-      fa = formula_auditor "foo", 'class Foo<Formula; url "file:///foo-1.0.tgz";end'
+    describe "#audit_github_repository" do
+      specify "#audit_github_repository when HOMEBREW_NO_GITHUB_API is set" do
+        ENV["HOMEBREW_NO_GITHUB_API"] = "1"
 
-      fa.audit_file
-      expect(fa.problems).to eq(["File should end with a newline"])
+        fa = formula_auditor "foo", <<~EOS, strict: true, online: true
+          class Foo < Formula
+            homepage "https://github.com/example/example"
+            url "http://example.com/foo-1.0.tgz"
+          end
+        EOS
+
+        fa.audit_github_repository
+        expect(fa.problems).to eq([])
+      end
     end
 
-    specify "no issue" do
-      fa = formula_auditor "foo", <<~EOS
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-          homepage "http://example.com"
-        end
-      EOS
+    describe "#audit_deps" do
+      describe "a dependency on a macOS-provided keg-only formula" do
+        describe "which is whitelisted" do
+          subject { fa }
 
-      fa.audit_file
-      expect(fa.problems).to eq([])
-    end
-  end
+          let(:fa) do
+            formula_auditor "foo", <<~EOS, new_formula: true
+              class Foo < Formula
+                url "http://example.com/foo-1.0.tgz"
+                homepage "http://example.com"
 
-  describe "#line_problems" do
-    specify "pkgshare" do
-      fa = formula_auditor "foo", <<~EOS, strict: true
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-        end
-      EOS
+                depends_on "openssl"
+              end
+            EOS
+          end
 
-      fa.line_problems 'ohai "#{share}/foo"', 3
-      expect(fa.problems.shift).to eq("Use \#{pkgshare} instead of \#{share}/foo")
-
-      fa.line_problems 'ohai "#{share}/foo/bar"', 3
-      expect(fa.problems.shift).to eq("Use \#{pkgshare} instead of \#{share}/foo")
-
-      fa.line_problems 'ohai share/"foo"', 3
-      expect(fa.problems.shift).to eq('Use pkgshare instead of (share/"foo")')
-
-      fa.line_problems 'ohai share/"foo/bar"', 3
-      expect(fa.problems.shift).to eq('Use pkgshare instead of (share/"foo")')
-
-      fa.line_problems 'ohai "#{share}/foo-bar"', 3
-      expect(fa.problems).to eq([])
-
-      fa.line_problems 'ohai share/"foo-bar"', 3
-      expect(fa.problems).to eq([])
-
-      fa.line_problems 'ohai share/"bar"', 3
-      expect(fa.problems).to eq([])
-    end
-
-    # Regression test for https://github.com/Homebrew/legacy-homebrew/pull/48744
-    # Formulae with "++" in their name would break various audit regexps:
-    #   Error: nested *?+ in regexp: /^libxml++3\s/
-    specify "++ in name" do
-      fa = formula_auditor "foolibc++", <<~EOS, strict: true
-        class Foolibcxx < Formula
-          desc "foolibc++ is a test"
-          url "http://example.com/foo-1.0.tgz"
-        end
-      EOS
-
-      fa.line_problems 'ohai "#{share}/foolibc++"', 3
-      expect(fa.problems.shift)
-        .to eq("Use \#{pkgshare} instead of \#{share}/foolibc++")
-
-      fa.line_problems 'ohai share/"foolibc++"', 3
-      expect(fa.problems.shift)
-        .to eq('Use pkgshare instead of (share/"foolibc++")')
-    end
-  end
-
-  describe "#audit_github_repository" do
-    specify "#audit_github_repository when HOMEBREW_NO_GITHUB_API is set" do
-      ENV["HOMEBREW_NO_GITHUB_API"] = "1"
-
-      fa = formula_auditor "foo", <<~EOS, strict: true, online: true
-        class Foo < Formula
-          homepage "https://github.com/example/example"
-          url "http://example.com/foo-1.0.tgz"
-        end
-      EOS
-
-      fa.audit_github_repository
-      expect(fa.problems).to eq([])
-    end
-  end
-
-  describe "#audit_deps" do
-    describe "a dependency on a macOS-provided keg-only formula" do
-      describe "which is whitelisted" do
-        subject { fa }
-
-        let(:fa) do
-          formula_auditor "foo", <<~EOS, new_formula: true
-            class Foo < Formula
-              url "http://example.com/foo-1.0.tgz"
+          let(:f_openssl) do
+            formula do
+              url "http://example.com/openssl-1.0.tgz"
               homepage "http://example.com"
 
-              depends_on "openssl"
+              keg_only :provided_by_macos
             end
-          EOS
-        end
-
-        let(:f_openssl) do
-          formula do
-            url "http://example.com/openssl-1.0.tgz"
-            homepage "http://example.com"
-
-            keg_only :provided_by_macos
           end
+
+          before do
+            allow(fa.formula.deps.first)
+              .to receive(:to_formula).and_return(f_openssl)
+            fa.audit_deps
+          end
+
+          its(:problems) { are_expected.to be_empty }
         end
 
-        before do
-          allow(fa.formula.deps.first)
-            .to receive(:to_formula).and_return(f_openssl)
-          fa.audit_deps
-        end
+        describe "which is not whitelisted" do
+          subject { fa }
 
-        its(:problems) { are_expected.to be_empty }
-      end
+          let(:fa) do
+            formula_auditor "foo", <<~EOS, new_formula: true
+              class Foo < Formula
+                url "http://example.com/foo-1.0.tgz"
+                homepage "http://example.com"
 
-      describe "which is not whitelisted" do
-        subject { fa }
+                depends_on "bc"
+              end
+            EOS
+          end
 
-        let(:fa) do
-          formula_auditor "foo", <<~EOS, new_formula: true
-            class Foo < Formula
-              url "http://example.com/foo-1.0.tgz"
+          let(:f_bc) do
+            formula do
+              url "http://example.com/bc-1.0.tgz"
               homepage "http://example.com"
 
-              depends_on "bc"
+              keg_only :provided_by_macos
             end
-          EOS
-        end
-
-        let(:f_bc) do
-          formula do
-            url "http://example.com/bc-1.0.tgz"
-            homepage "http://example.com"
-
-            keg_only :provided_by_macos
           end
+
+          before do
+            allow(fa.formula.deps.first)
+              .to receive(:to_formula).and_return(f_bc)
+            fa.audit_deps
+          end
+
+          its(:problems) { are_expected.to match([/unnecessary/]) }
         end
-
-        before do
-          allow(fa.formula.deps.first)
-            .to receive(:to_formula).and_return(f_bc)
-          fa.audit_deps
-        end
-
-        its(:problems) { are_expected.to match([/unnecessary/]) }
-      end
-    end
-  end
-
-  describe "#audit_keg_only_style" do
-    specify "keg_only_needs_downcasing" do
-      fa = formula_auditor "foo", <<~EOS, strict: true
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-
-          keg_only "Because why not"
-        end
-      EOS
-
-      fa.audit_keg_only_style
-      expect(fa.problems)
-        .to eq(["'Because' from the keg_only reason should be 'because'.\n"])
-    end
-
-    specify "keg_only_redundant_period" do
-      fa = formula_auditor "foo", <<~EOS, strict: true
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-
-          keg_only "because this line ends in a period."
-        end
-      EOS
-
-      fa.audit_keg_only_style
-      expect(fa.problems)
-        .to eq(["keg_only reason should not end with a period."])
-    end
-
-    specify "keg_only_handles_block_correctly" do
-      fa = formula_auditor "foo", <<~EOS, strict: true
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-
-          keg_only <<~EOF
-            this line starts with a lowercase word.
-
-            This line does not but that shouldn't be a
-            problem
-          EOF
-        end
-      EOS
-
-      fa.audit_keg_only_style
-      expect(fa.problems)
-        .to eq([])
-    end
-
-    specify "keg_only_handles_whitelist_correctly" do
-      fa = formula_auditor "foo", <<~EOS, strict: true
-        class Foo < Formula
-          url "http://example.com/foo-1.0.tgz"
-
-          keg_only "Apple ships foo in the CLT package"
-        end
-      EOS
-
-      fa.audit_keg_only_style
-      expect(fa.problems)
-        .to eq([])
-    end
-  end
-
-  describe "#audit_revision_and_version_scheme" do
-    subject do
-      fa = described_class.new(Formulary.factory(formula_path))
-      fa.audit_revision_and_version_scheme
-      fa.problems.first
-    end
-
-    let(:origin_tap_path) { Tap::TAP_DIRECTORY/"homebrew/homebrew-foo" }
-    let(:formula_subpath) { "Formula/foo#{@foo_version}.rb" }
-    let(:origin_formula_path) { origin_tap_path/formula_subpath }
-    let(:tap_path) { Tap::TAP_DIRECTORY/"homebrew/homebrew-bar" }
-    let(:formula_path) { tap_path/formula_subpath }
-
-    before do
-      @foo_version = Count.increment
-
-      origin_formula_path.write <<~EOS
-        class Foo#{@foo_version} < Formula
-          url "https://example.com/foo-1.0.tar.gz"
-          revision 2
-          version_scheme 1
-        end
-      EOS
-
-      origin_tap_path.mkpath
-      origin_tap_path.cd do
-        system "git", "init"
-        system "git", "add", "--all"
-        system "git", "commit", "-m", "init"
-      end
-
-      tap_path.mkpath
-      tap_path.cd do
-        system "git", "clone", origin_tap_path, "."
       end
     end
 
-    def formula_gsub(before, after = "")
-      text = formula_path.read
-      text.gsub! before, after
-      formula_path.unlink
-      formula_path.write text
-    end
+    describe "#audit_keg_only_style" do
+      specify "keg_only_needs_downcasing" do
+        fa = formula_auditor "foo", <<~EOS, strict: true
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
 
-    def formula_gsub_commit(before, after = "")
-      text = origin_formula_path.read
-      text.gsub!(before, after)
-      origin_formula_path.unlink
-      origin_formula_path.write text
+            keg_only "Because why not"
+          end
+        EOS
 
-      origin_tap_path.cd do
-        system "git", "commit", "-am", "commit"
+        fa.audit_keg_only_style
+        expect(fa.problems)
+          .to eq(["'Because' from the keg_only reason should be 'because'.\n"])
       end
 
-      tap_path.cd do
-        system "git", "fetch"
-        system "git", "reset", "--hard", "origin/master"
+      specify "keg_only_redundant_period" do
+        fa = formula_auditor "foo", <<~EOS, strict: true
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+
+            keg_only "because this line ends in a period."
+          end
+        EOS
+
+        fa.audit_keg_only_style
+        expect(fa.problems)
+          .to eq(["keg_only reason should not end with a period."])
+      end
+
+      specify "keg_only_handles_block_correctly" do
+        fa = formula_auditor "foo", <<~EOS, strict: true
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+
+            keg_only <<~EOF
+              this line starts with a lowercase word.
+
+              This line does not but that shouldn't be a
+              problem
+            EOF
+          end
+        EOS
+
+        fa.audit_keg_only_style
+        expect(fa.problems)
+          .to eq([])
+      end
+
+      specify "keg_only_handles_whitelist_correctly" do
+        fa = formula_auditor "foo", <<~EOS, strict: true
+          class Foo < Formula
+            url "http://example.com/foo-1.0.tgz"
+
+            keg_only "Apple ships foo in the CLT package"
+          end
+        EOS
+
+        fa.audit_keg_only_style
+        expect(fa.problems)
+          .to eq([])
       end
     end
 
-    context "revisions" do
-      context "should not be removed when first committed above 0" do
-        it { is_expected.to be_nil }
+    describe "#audit_revision_and_version_scheme" do
+      subject do
+        fa = described_class.new(Formulary.factory(formula_path))
+        fa.audit_revision_and_version_scheme
+        fa.problems.first
       end
 
-      context "should not decrease with the same version" do
-        before { formula_gsub_commit "revision 2", "revision 1" }
+      let(:origin_tap_path) { Tap::TAP_DIRECTORY/"homebrew/homebrew-foo" }
+      let(:formula_subpath) { "Formula/foo#{@foo_version}.rb" }
+      let(:origin_formula_path) { origin_tap_path/formula_subpath }
+      let(:tap_path) { Tap::TAP_DIRECTORY/"homebrew/homebrew-bar" }
+      let(:formula_path) { tap_path/formula_subpath }
 
-        it { is_expected.to match("revision should not decrease (from 2 to 1)") }
-      end
+      before do
+        @foo_version = Count.increment
 
-      context "should not be removed with the same version" do
-        before { formula_gsub_commit "revision 2" }
+        origin_formula_path.write <<~EOS
+          class Foo#{@foo_version} < Formula
+            url "https://example.com/foo-1.0.tar.gz"
+            revision 2
+            version_scheme 1
+          end
+        EOS
 
-        it { is_expected.to match("revision should not decrease (from 2 to 0)") }
-      end
-
-      context "should not decrease with the same, uncommitted version" do
-        before { formula_gsub "revision 2", "revision 1" }
-
-        it { is_expected.to match("revision should not decrease (from 2 to 1)") }
-      end
-
-      context "should be removed with a newer version" do
-        before { formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz" }
-
-        it { is_expected.to match("'revision 2' should be removed") }
-      end
-
-      context "should not warn on an newer version revision removal" do
-        before do
-          formula_gsub_commit "revision 2", ""
-          formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+        origin_tap_path.mkpath
+        origin_tap_path.cd do
+          system "git", "init"
+          system "git", "add", "--all"
+          system "git", "commit", "-m", "init"
         end
 
-        it { is_expected.to be_nil }
+        tap_path.mkpath
+        tap_path.cd do
+          system "git", "clone", origin_tap_path, "."
+        end
       end
 
-      context "should only increment by 1 with an uncommitted version" do
-        before do
-          formula_gsub "foo-1.0.tar.gz", "foo-1.1.tar.gz"
-          formula_gsub "revision 2", "revision 4"
-        end
-
-        it { is_expected.to match("revisions should only increment by 1") }
+      def formula_gsub(before, after = "")
+        text = formula_path.read
+        text.gsub! before, after
+        formula_path.unlink
+        formula_path.write text
       end
 
-      context "should not warn on past increment by more than 1" do
-        before do
-          formula_gsub_commit "revision 2", "# no revision"
-          formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
-          formula_gsub_commit "# no revision", "revision 3"
+      def formula_gsub_commit(before, after = "")
+        text = origin_formula_path.read
+        text.gsub!(before, after)
+        origin_formula_path.unlink
+        origin_formula_path.write text
+
+        origin_tap_path.cd do
+          system "git", "commit", "-am", "commit"
         end
 
-        it { is_expected.to be_nil }
+        tap_path.cd do
+          system "git", "fetch"
+          system "git", "reset", "--hard", "origin/master"
+        end
+      end
+
+      context "revisions" do
+        context "should not be removed when first committed above 0" do
+          it { is_expected.to be_nil }
+        end
+
+        context "should not decrease with the same version" do
+          before { formula_gsub_commit "revision 2", "revision 1" }
+
+          it { is_expected.to match("revision should not decrease (from 2 to 1)") }
+        end
+
+        context "should not be removed with the same version" do
+          before { formula_gsub_commit "revision 2" }
+
+          it { is_expected.to match("revision should not decrease (from 2 to 0)") }
+        end
+
+        context "should not decrease with the same, uncommitted version" do
+          before { formula_gsub "revision 2", "revision 1" }
+
+          it { is_expected.to match("revision should not decrease (from 2 to 1)") }
+        end
+
+        context "should be removed with a newer version" do
+          before { formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz" }
+
+          it { is_expected.to match("'revision 2' should be removed") }
+        end
+
+        context "should not warn on an newer version revision removal" do
+          before do
+            formula_gsub_commit "revision 2", ""
+            formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+          end
+
+          it { is_expected.to be_nil }
+        end
+
+        context "should only increment by 1 with an uncommitted version" do
+          before do
+            formula_gsub "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+            formula_gsub "revision 2", "revision 4"
+          end
+
+          it { is_expected.to match("revisions should only increment by 1") }
+        end
+
+        context "should not warn on past increment by more than 1" do
+          before do
+            formula_gsub_commit "revision 2", "# no revision"
+            formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+            formula_gsub_commit "# no revision", "revision 3"
+          end
+
+          it { is_expected.to be_nil }
+        end
+      end
+
+      context "version_schemes" do
+        context "should not decrease with the same version" do
+          before { formula_gsub_commit "version_scheme 1" }
+
+          it { is_expected.to match("version_scheme should not decrease (from 1 to 0)") }
+        end
+
+        context "should not decrease with a new version" do
+          before do
+            formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+            formula_gsub_commit "version_scheme 1", ""
+            formula_gsub_commit "revision 2", ""
+          end
+
+          it { is_expected.to match("version_scheme should not decrease (from 1 to 0)") }
+        end
+
+        context "should only increment by 1" do
+          before do
+            formula_gsub_commit "version_scheme 1", "# no version_scheme"
+            formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
+            formula_gsub_commit "revision 2", ""
+            formula_gsub_commit "# no version_scheme", "version_scheme 3"
+          end
+
+          it { is_expected.to match("version_schemes should only increment by 1") }
+        end
+      end
+
+      context "versions" do
+        context "uncommitted should not decrease" do
+          before { formula_gsub "foo-1.0.tar.gz", "foo-0.9.tar.gz" }
+
+          it { is_expected.to match("stable version should not decrease (from 1.0 to 0.9)") }
+        end
+
+        context "committed can decrease" do
+          before do
+            formula_gsub_commit "revision 2"
+            formula_gsub_commit "foo-1.0.tar.gz", "foo-0.9.tar.gz"
+          end
+
+          it { is_expected.to be_nil }
+        end
+
+        context "can decrease with version_scheme increased" do
+          before do
+            formula_gsub "revision 2"
+            formula_gsub "foo-1.0.tar.gz", "foo-0.9.tar.gz"
+            formula_gsub "version_scheme 1", "version_scheme 2"
+          end
+
+          it { is_expected.to be_nil }
+        end
       end
     end
 
-    context "version_schemes" do
-      context "should not decrease with the same version" do
-        before { formula_gsub_commit "version_scheme 1" }
-
-        it { is_expected.to match("version_scheme should not decrease (from 1 to 0)") }
-      end
-
-      context "should not decrease with a new version" do
-        before do
-          formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
-          formula_gsub_commit "version_scheme 1", ""
-          formula_gsub_commit "revision 2", ""
-        end
-
-        it { is_expected.to match("version_scheme should not decrease (from 1 to 0)") }
-      end
-
-      context "should only increment by 1" do
-        before do
-          formula_gsub_commit "version_scheme 1", "# no version_scheme"
-          formula_gsub_commit "foo-1.0.tar.gz", "foo-1.1.tar.gz"
-          formula_gsub_commit "revision 2", ""
-          formula_gsub_commit "# no version_scheme", "version_scheme 3"
-        end
-
-        it { is_expected.to match("version_schemes should only increment by 1") }
-      end
-    end
-
-    context "versions" do
-      context "uncommitted should not decrease" do
-        before { formula_gsub "foo-1.0.tar.gz", "foo-0.9.tar.gz" }
-
-        it { is_expected.to match("stable version should not decrease (from 1.0 to 0.9)") }
-      end
-
-      context "committed can decrease" do
-        before do
-          formula_gsub_commit "revision 2"
-          formula_gsub_commit "foo-1.0.tar.gz", "foo-0.9.tar.gz"
-        end
-
-        it { is_expected.to be_nil }
-      end
-
-      context "can decrease with version_scheme increased" do
-        before do
-          formula_gsub "revision 2"
-          formula_gsub "foo-1.0.tar.gz", "foo-0.9.tar.gz"
-          formula_gsub "version_scheme 1", "version_scheme 2"
-        end
-
-        it { is_expected.to be_nil }
-      end
-    end
-  end
-
-  describe "#audit_url_is_not_binary" do
-    specify "it detects a url containing darwin and x86_64" do
-      fa = formula_auditor "foo", <<~EOS, official_tap: true
-        class Foo < Formula
-          url "https://example.com/example-darwin.x86_64.tar.gz"
-        end
-      EOS
-
-      fa.audit_url_is_not_binary
-
-      expect(fa.problems.first)
-        .to match("looks like a binary package, not a source archive. Official taps are source-only.")
-    end
-
-    specify "it detects a url containing darwin and amd64" do
-      fa = formula_auditor "foo", <<~EOS, official_tap: true
-        class Foo < Formula
-          url "https://example.com/example-darwin.amd64.tar.gz"
-        end
-      EOS
-
-      fa.audit_url_is_not_binary
-
-      expect(fa.problems.first)
-        .to match("looks like a binary package, not a source archive. Official taps are source-only.")
-    end
-
-    specify "it works on the devel spec" do
-      fa = formula_auditor "foo", <<~EOS, official_tap: true
-        class Foo < Formula
-          url "https://example.com/valid-1.0.tar.gz"
-
-          devel do
+    describe "#audit_url_is_not_binary" do
+      specify "it detects a url containing darwin and x86_64" do
+        fa = formula_auditor "foo", <<~EOS, official_tap: true
+          class Foo < Formula
             url "https://example.com/example-darwin.x86_64.tar.gz"
           end
-        end
-      EOS
+        EOS
 
-      fa.audit_url_is_not_binary
+        fa.audit_url_is_not_binary
 
-      expect(fa.problems.first)
-        .to match("looks like a binary package, not a source archive. Official taps are source-only.")
-    end
+        expect(fa.problems.first)
+          .to match("looks like a binary package, not a source archive. Official taps are source-only.")
+      end
 
-    specify "it works on the head spec" do
-      fa = formula_auditor "foo", <<~EOS, official_tap: true
-        class Foo < Formula
-          url "https://example.com/valid-1.0.tar.gz"
-
-          head do
-            url "https://example.com/example-darwin.x86_64.tar.gz"
+      specify "it detects a url containing darwin and amd64" do
+        fa = formula_auditor "foo", <<~EOS, official_tap: true
+          class Foo < Formula
+            url "https://example.com/example-darwin.amd64.tar.gz"
           end
-        end
-      EOS
+        EOS
 
-      fa.audit_url_is_not_binary
+        fa.audit_url_is_not_binary
 
-      expect(fa.problems.first)
-        .to match("looks like a binary package, not a source archive. Official taps are source-only.")
-    end
+        expect(fa.problems.first)
+          .to match("looks like a binary package, not a source archive. Official taps are source-only.")
+      end
 
-    specify "it ignores resource urls" do
-      fa = formula_auditor "foo", <<~EOS, official_tap: true
-        class Foo < Formula
-          url "https://example.com/valid-1.0.tar.gz"
+      specify "it works on the devel spec" do
+        fa = formula_auditor "foo", <<~EOS, official_tap: true
+          class Foo < Formula
+            url "https://example.com/valid-1.0.tar.gz"
 
-          resource "binary_res" do
-            url "https://example.com/example-darwin.x86_64.tar.gz"
+            devel do
+              url "https://example.com/example-darwin.x86_64.tar.gz"
+            end
           end
-        end
-      EOS
+        EOS
 
-      fa.audit_url_is_not_binary
+        fa.audit_url_is_not_binary
 
-      expect(fa.problems).to eq([])
+        expect(fa.problems.first)
+          .to match("looks like a binary package, not a source archive. Official taps are source-only.")
+      end
+
+      specify "it works on the head spec" do
+        fa = formula_auditor "foo", <<~EOS, official_tap: true
+          class Foo < Formula
+            url "https://example.com/valid-1.0.tar.gz"
+
+            head do
+              url "https://example.com/example-darwin.x86_64.tar.gz"
+            end
+          end
+        EOS
+
+        fa.audit_url_is_not_binary
+
+        expect(fa.problems.first)
+          .to match("looks like a binary package, not a source archive. Official taps are source-only.")
+      end
+
+      specify "it ignores resource urls" do
+        fa = formula_auditor "foo", <<~EOS, official_tap: true
+          class Foo < Formula
+            url "https://example.com/valid-1.0.tar.gz"
+
+            resource "binary_res" do
+              url "https://example.com/example-darwin.x86_64.tar.gz"
+            end
+          end
+        EOS
+
+        fa.audit_url_is_not_binary
+
+        expect(fa.problems).to eq([])
+      end
     end
   end
 end
diff --git a/Library/Homebrew/test/dev-cmd/tap_spec.rb b/Library/Homebrew/test/dev-cmd/tap_spec.rb
index d09d0245f3..de9c3d891e 100644
--- a/Library/Homebrew/test/dev-cmd/tap_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/tap_spec.rb
@@ -15,11 +15,6 @@ describe "brew tap", :integration_test do
       .and not_to_output.to_stderr
       .and be_a_success
 
-    expect { brew "tap", "--list-official" }
-      .to output(%r{homebrew/php}).to_stdout
-      .and not_to_output.to_stderr
-      .and be_a_success
-
     expect { brew "tap-info" }
       .to output(/2 taps/).to_stdout
       .and not_to_output.to_stderr
@@ -60,11 +55,26 @@ describe "brew tap", :integration_test do
       .and not_to_output.to_stderr
       .and be_a_success
 
+    expect { brew "tap", "--force-auto-update", "homebrew/bar", path/".git" }
+      .to output(/Tapped/).to_stdout
+      .and output(/Cloning/).to_stderr
+      .and be_a_success
+
+    expect { brew "untap", "homebrew/bar" }
+      .to output(/Untapped/).to_stdout
+      .and not_to_output.to_stderr
+      .and be_a_success
+
     expect { brew "tap", "homebrew/bar", path/".git", "-q", "--full" }
       .to be_a_success
       .and not_to_output.to_stdout
       .and not_to_output.to_stderr
 
+    expect { brew "tap", "--force-auto-update", "homebrew/bar" }
+      .to be_a_success
+      .and not_to_output.to_stdout
+      .and not_to_output.to_stderr
+
     expect { brew "untap", "homebrew/bar" }
       .to output(/Untapped/).to_stdout
       .and not_to_output.to_stderr
diff --git a/Library/Homebrew/test/diagnostic_spec.rb b/Library/Homebrew/test/diagnostic_spec.rb
index f347010a93..52e7d3a392 100644
--- a/Library/Homebrew/test/diagnostic_spec.rb
+++ b/Library/Homebrew/test/diagnostic_spec.rb
@@ -6,12 +6,6 @@ describe Homebrew::Diagnostic::Checks do
     expect(subject.inject_file_list(%w[/a /b], "foo:\n")).to eq("foo:\n  /a\n  /b\n")
   end
 
-  specify "#check_path_for_trailing_slashes" do
-    ENV["HOMEBREW_PATH"] += File::PATH_SEPARATOR + "/foo/bar/"
-    expect(subject.check_path_for_trailing_slashes)
-      .to match("Some directories in your path end in a slash")
-  end
-
   specify "#check_build_from_source" do
     ENV["HOMEBREW_BUILD_FROM_SOURCE"] = "1"
     expect(subject.check_build_from_source)
@@ -137,15 +131,6 @@ describe Homebrew::Diagnostic::Checks do
     end
   end
 
-  specify "#check_user_curlrc" do
-    mktmpdir do |path|
-      FileUtils.touch "#{path}/.curlrc"
-      ENV["CURL_HOME"] = path
-
-      expect(subject.check_user_curlrc).to match("You have a curlrc file")
-    end
-  end
-
   specify "#check_for_config_scripts" do
     mktmpdir do |path|
       file = "#{path}/foo-config"
diff --git a/Library/Homebrew/test/download_strategies_spec.rb b/Library/Homebrew/test/download_strategies_spec.rb
index 08bbb58e89..f4857787ef 100644
--- a/Library/Homebrew/test/download_strategies_spec.rb
+++ b/Library/Homebrew/test/download_strategies_spec.rb
@@ -268,6 +268,90 @@ describe CurlDownloadStrategy do
   end
 end
 
+describe ScpDownloadStrategy do
+  def resource_for(url)
+    double(Resource, url: url, mirrors: [], specs: {}, version: nil)
+  end
+
+  subject { described_class.new(name, resource) }
+  let(:name) { "foo" }
+  let(:url) { "scp://example.com/foo.tar.gz" }
+  let(:resource) { resource_for(url) }
+
+  describe "#initialize" do
+    invalid_urls = %w[
+      http://example.com/foo.tar.gz
+      scp://@example.com/foo.tar.gz
+      scp://example.com:/foo.tar.gz
+      scp://example.com
+    ]
+
+    invalid_urls.each do |invalid_url|
+      context "with invalid URL #{invalid_url}" do
+        it "raises ScpDownloadStrategyError" do
+          expect {
+            described_class.new(name, resource_for(invalid_url))
+          }.to raise_error(ScpDownloadStrategyError)
+        end
+      end
+    end
+  end
+
+  describe "#fetch" do
+    before do
+      expect(subject.temporary_path).to receive(:rename).and_return(true)
+    end
+
+    context "when given a valid URL" do
+      let(:url) { "scp://example.com/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with a username" do
+      let(:url) { "scp://user@example.com/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "user@example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with a port" do
+      let(:url) { "scp://example.com:1234/foo.tar.gz" }
+      it "copies the file via scp" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "-P 1234 example.com:/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+
+    context "when given a URL with /~/" do
+      let(:url) { "scp://example.com/~/foo.tar.gz" }
+      it "treats the path as relative to the home directory" do
+        expect(subject)
+          .to receive(:safe_system)
+          .with("scp", "example.com:~/foo.tar.gz", anything)
+          .and_return(true)
+
+        subject.fetch
+      end
+    end
+  end
+end
+
 describe DownloadStrategyDetector do
   describe "::detect" do
     subject { described_class.detect(url, strategy) }
@@ -306,6 +390,11 @@ describe DownloadStrategyDetector do
       end
     end
 
+    context "when given an scp URL" do
+      let(:url) { "scp://example.com/brew.tar.gz" }
+      it { is_expected.to eq(ScpDownloadStrategy) }
+    end
+
     it "defaults to cURL" do
       expect(subject).to eq(CurlDownloadStrategy)
     end
diff --git a/Library/Homebrew/test/formulary_spec.rb b/Library/Homebrew/test/formulary_spec.rb
index 87124c60ce..2beaed5e34 100644
--- a/Library/Homebrew/test/formulary_spec.rb
+++ b/Library/Homebrew/test/formulary_spec.rb
@@ -7,7 +7,7 @@ describe Formulary do
   let(:formula_path) { CoreTap.new.formula_dir/"#{formula_name}.rb" }
   let(:formula_content) do
     <<~EOS
-      class #{subject.class_s(formula_name)} < Formula
+      class #{described_class.class_s(formula_name)} < Formula
         url "file://#{TEST_FIXTURE_DIR}/tarballs/testball-0.1.tbz"
         sha256 TESTBALL_SHA256
 
@@ -29,18 +29,27 @@ describe Formulary do
 
   describe "::class_s" do
     it "replaces '+' with 'x'" do
-      expect(subject.class_s("foo++")).to eq("Fooxx")
+      expect(described_class.class_s("foo++")).to eq("Fooxx")
     end
 
-    it "converts a string to PascalCase" do
-      expect(subject.class_s("shell.fm")).to eq("ShellFm")
-      expect(subject.class_s("s-lang")).to eq("SLang")
-      expect(subject.class_s("pkg-config")).to eq("PkgConfig")
-      expect(subject.class_s("foo_bar")).to eq("FooBar")
+    it "converts a string with dots to PascalCase" do
+      expect(described_class.class_s("shell.fm")).to eq("ShellFm")
+    end
+
+    it "converts a string with hyphens to PascalCase" do
+      expect(described_class.class_s("pkg-config")).to eq("PkgConfig")
+    end
+
+    it "converts a string with a single letter separated by a hyphen to PascalCase" do
+      expect(described_class.class_s("s-lang")).to eq("SLang")
+    end
+
+    it "converts a string with underscores to PascalCase" do
+      expect(described_class.class_s("foo_bar")).to eq("FooBar")
     end
 
     it "replaces '@' with 'AT'" do
-      expect(subject.class_s("openssl@1.1")).to eq("OpensslAT11")
+      expect(described_class.class_s("openssl@1.1")).to eq("OpensslAT11")
     end
   end
 
@@ -50,134 +59,162 @@ describe Formulary do
     end
 
     it "returns a Formula" do
-      expect(subject.factory(formula_name)).to be_kind_of(Formula)
+      expect(described_class.factory(formula_name)).to be_kind_of(Formula)
     end
 
     it "returns a Formula when given a fully qualified name" do
-      expect(subject.factory("homebrew/core/#{formula_name}")).to be_kind_of(Formula)
+      expect(described_class.factory("homebrew/core/#{formula_name}")).to be_kind_of(Formula)
     end
 
     it "raises an error if the Formula cannot be found" do
       expect {
-        subject.factory("not_existed_formula")
+        described_class.factory("not_existed_formula")
       }.to raise_error(FormulaUnavailableError)
     end
 
-    context "if the Formula has the wrong class" do
+    context "when the Formula has the wrong class" do
       let(:formula_name) { "giraffe" }
       let(:formula_content) do
         <<~EOS
-          class Wrong#{subject.class_s(formula_name)} < Formula
+          class Wrong#{described_class.class_s(formula_name)} < Formula
           end
         EOS
       end
 
       it "raises an error" do
         expect {
-          subject.factory(formula_name)
+          described_class.factory(formula_name)
         }.to raise_error(FormulaClassUnavailableError)
       end
     end
 
     it "returns a Formula when given a path" do
-      expect(subject.factory(formula_path)).to be_kind_of(Formula)
+      expect(described_class.factory(formula_path)).to be_kind_of(Formula)
     end
 
     it "returns a Formula when given a URL" do
-      formula = subject.factory("file://#{formula_path}")
+      formula = described_class.factory("file://#{formula_path}")
       expect(formula).to be_kind_of(Formula)
     end
 
-    it "returns a Formula when given a bottle" do
-      formula = subject.factory(bottle)
-      expect(formula).to be_kind_of(Formula)
-      expect(formula.local_bottle_path).to eq(bottle.realpath)
+    context "when given a bottle" do
+      subject(:formula) { described_class.factory(bottle) }
+
+      it "returns a Formula" do
+        expect(formula).to be_kind_of(Formula)
+      end
+
+      it "calling #local_bottle_path on the returned Formula returns the bottle path" do
+        expect(formula.local_bottle_path).to eq(bottle.realpath)
+      end
     end
 
-    it "returns a Formula when given an alias" do
-      alias_dir = CoreTap.instance.alias_dir
-      alias_dir.mkpath
-      alias_path = alias_dir/"foo"
-      FileUtils.ln_s formula_path, alias_path
-      result = subject.factory("foo")
-      expect(result).to be_kind_of(Formula)
-      expect(result.alias_path).to eq(alias_path.to_s)
+    context "when given an alias" do
+      subject(:formula) { described_class.factory("foo") }
+
+      let(:alias_dir) { CoreTap.instance.alias_dir.tap(&:mkpath) }
+      let(:alias_path) { alias_dir/"foo" }
+
+      before do
+        alias_dir.mkpath
+        FileUtils.ln_s formula_path, alias_path
+      end
+
+      it "returns a Formula" do
+        expect(formula).to be_kind_of(Formula)
+      end
+
+      it "calling #alias_path on the returned Formula returns the alias path" do
+        expect(formula.alias_path).to eq(alias_path.to_s)
+      end
     end
 
     context "with installed Formula" do
-      let(:formula) { subject.factory(formula_path) }
+      let(:formula) { described_class.factory(formula_path) }
       let(:installer) { FormulaInstaller.new(formula) }
 
       it "returns a Formula when given a rack" do
         installer.install
 
-        f = subject.from_rack(formula.rack)
+        f = described_class.from_rack(formula.rack)
         expect(f).to be_kind_of(Formula)
-        expect(f.build).to be_kind_of(Tab)
       end
 
       it "returns a Formula when given a Keg" do
         installer.install
 
         keg = Keg.new(formula.prefix)
-        f = subject.from_keg(keg)
+        f = described_class.from_keg(keg)
         expect(f).to be_kind_of(Formula)
-        expect(f.build).to be_kind_of(Tab)
       end
     end
 
-    context "from Tap" do
+    context "when loading from Tap" do
       let(:tap) { Tap.new("homebrew", "foo") }
+      let(:another_tap) { Tap.new("homebrew", "bar") }
       let(:formula_path) { tap.path/"#{formula_name}.rb" }
 
       it "returns a Formula when given a name" do
-        expect(subject.factory(formula_name)).to be_kind_of(Formula)
+        expect(described_class.factory(formula_name)).to be_kind_of(Formula)
       end
 
       it "returns a Formula from an Alias path" do
         alias_dir = tap.path/"Aliases"
         alias_dir.mkpath
         FileUtils.ln_s formula_path, alias_dir/"bar"
-        expect(subject.factory("bar")).to be_kind_of(Formula)
+        expect(described_class.factory("bar")).to be_kind_of(Formula)
       end
 
       it "raises an error when the Formula cannot be found" do
         expect {
-          subject.factory("#{tap}/not_existed_formula")
+          described_class.factory("#{tap}/not_existed_formula")
         }.to raise_error(TapFormulaUnavailableError)
       end
 
       it "returns a Formula when given a fully qualified name" do
-        expect(subject.factory("#{tap}/#{formula_name}")).to be_kind_of(Formula)
+        expect(described_class.factory("#{tap}/#{formula_name}")).to be_kind_of(Formula)
       end
 
       it "raises an error if a Formula is in multiple Taps" do
-        begin
-          another_tap = Tap.new("homebrew", "bar")
-          (another_tap.path/"#{formula_name}.rb").write formula_content
-          expect {
-            subject.factory(formula_name)
-          }.to raise_error(TapFormulaAmbiguityError)
-        ensure
-          another_tap.path.rmtree
-        end
+        (another_tap.path/"#{formula_name}.rb").write formula_content
+
+        expect {
+          described_class.factory(formula_name)
+        }.to raise_error(TapFormulaAmbiguityError)
       end
     end
   end
 
   specify "::from_contents" do
-    expect(subject.from_contents(formula_name, formula_path, formula_content)).to be_kind_of(Formula)
+    expect(described_class.from_contents(formula_name, formula_path, formula_content)).to be_kind_of(Formula)
   end
 
-  specify "::to_rack" do
-    expect(subject.to_rack(formula_name)).to eq(HOMEBREW_CELLAR/formula_name)
+  describe "::to_rack" do
+    alias_matcher :exist, :be_exist
 
-    (HOMEBREW_CELLAR/formula_name).mkpath
-    expect(subject.to_rack(formula_name)).to eq(HOMEBREW_CELLAR/formula_name)
+    let(:rack_path) { HOMEBREW_CELLAR/formula_name }
 
-    expect {
-      subject.to_rack("a/b/#{formula_name}")
-    }.to raise_error(TapFormulaUnavailableError)
+    context "when the Rack does not exist" do
+      it "returns the Rack" do
+        expect(described_class.to_rack(formula_name)).to eq(rack_path)
+      end
+    end
+
+    context "when the Rack exists" do
+      before do
+        rack_path.mkpath
+      end
+
+      it "returns the Rack" do
+        expect(described_class.to_rack(formula_name)).to eq(rack_path)
+      end
+    end
+
+    it "raises an error if the Formula is not available" do
+      expect {
+        described_class.to_rack("a/b/#{formula_name}")
+      }.to raise_error(TapFormulaUnavailableError)
+    end
   end
 
   describe "::find_with_priority" do
@@ -191,27 +228,21 @@ describe Formulary do
     end
 
     it "prioritizes core Formulae" do
-      formula = subject.find_with_priority(formula_name)
-      expect(formula).to be_kind_of(Formula)
+      formula = described_class.find_with_priority(formula_name)
       expect(formula.path).to eq(core_path)
     end
 
     it "prioritizes Formulae from pinned Taps" do
-      begin
-        tap.pin
-        formula = subject.find_with_priority(formula_name)
-        expect(formula).to be_kind_of(Formula)
-        expect(formula.path).to eq(tap_path.realpath)
-      ensure
-        tap.pinned_symlink_path.parent.parent.rmtree
-      end
+      tap.pin
+      formula = described_class.find_with_priority(formula_name)
+      expect(formula.path).to eq(tap_path.realpath)
     end
   end
 
   describe "::core_path" do
     it "returns the path to a Formula in the core tap" do
       name = "foo-bar"
-      expect(subject.core_path(name))
+      expect(described_class.core_path(name))
         .to eq(Pathname.new("#{HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-core/Formula/#{name}.rb"))
     end
   end
diff --git a/Library/Homebrew/test/hardware/cpu_spec.rb b/Library/Homebrew/test/hardware/cpu_spec.rb
new file mode 100644
index 0000000000..5bcb9fca5c
--- /dev/null
+++ b/Library/Homebrew/test/hardware/cpu_spec.rb
@@ -0,0 +1,114 @@
+require "hardware"
+
+describe Hardware::CPU do
+  describe "::type" do
+    let(:cpu_types) {
+      [
+        :intel,
+        :ppc,
+        :dunno,
+      ]
+    }
+
+    it "returns the current CPU's type as a symbol, or :dunno if it cannot be detected" do
+      expect(cpu_types).to include(described_class.type)
+    end
+  end
+
+  describe "::family" do
+    let(:cpu_families) {
+      [
+        :core,
+        :core2,
+        :penryn,
+        :nehalem,
+        :arrandale,
+        :sandybridge,
+        :ivybridge,
+        :haswell,
+        :broadwell,
+        :skylake,
+        :kabylake,
+        :dunno,
+      ]
+    }
+
+    it "returns the current CPU's family name as a symbol, or :dunno if it cannot be detected" do
+      expect(cpu_families).to include described_class.family
+    end
+  end
+
+  describe "::can_run?" do
+    subject { described_class }
+
+    matcher :be_able_to_run do |arch|
+      match do |expected|
+        allow(expected).to receive(:type).and_return type
+        allow(expected).to receive(:bits).and_return bits
+
+        expect(expected.can_run?(arch)).to be true
+      end
+    end
+
+    let(:type) { described_class.type }
+    let(:bits) { described_class.bits }
+
+    before do
+      allow(described_class).to receive(:type).and_return type
+      allow(described_class).to receive(:bits).and_return bits
+    end
+
+    context "when on an 32-bit Intel machine" do
+      let(:type) { :intel }
+      let(:bits) { 32 }
+
+      it { is_expected.to be_able_to_run :i386 }
+      it { is_expected.not_to be_able_to_run :x86_64 }
+      it { is_expected.not_to be_able_to_run :ppc32 }
+      it { is_expected.not_to be_able_to_run :ppc64 }
+    end
+
+    context "when on an 64-bit Intel machine" do
+      let(:type) { :intel }
+      let(:bits) { 64 }
+
+      it { is_expected.to be_able_to_run :i386 }
+      it { is_expected.to be_able_to_run :x86_64 }
+      it { is_expected.not_to be_able_to_run :ppc32 }
+      it { is_expected.not_to be_able_to_run :ppc64 }
+    end
+
+    context "when on a 32-bit PowerPC machine" do
+      let(:type) { :ppc }
+      let(:bits) { 32 }
+
+      it { is_expected.not_to be_able_to_run :i386 }
+      it { is_expected.not_to be_able_to_run :x86_64 }
+      it { is_expected.to be_able_to_run :ppc32 }
+      it { is_expected.not_to be_able_to_run :ppc64 }
+    end
+
+    context "when on a 64-bit PowerPC machine" do
+      let(:type) { :ppc }
+      let(:bits) { 64 }
+
+      it { is_expected.not_to be_able_to_run :i386 }
+      it { is_expected.not_to be_able_to_run :x86_64 }
+      it { is_expected.to be_able_to_run :ppc32 }
+      it { is_expected.to be_able_to_run :ppc64 }
+    end
+
+    context "when the CPU type is unknown" do
+      let(:type) { :dunno }
+
+      it { is_expected.not_to be_able_to_run :i386 }
+      it { is_expected.not_to be_able_to_run :x86_64 }
+      it { is_expected.not_to be_able_to_run :ppc32 }
+      it { is_expected.not_to be_able_to_run :ppc64 }
+    end
+
+    context "when the architecture is unknown" do
+      it { is_expected.not_to be_able_to_run :blah }
+    end
+  end
+end
diff --git a/Library/Homebrew/test/hardware_spec.rb b/Library/Homebrew/test/hardware_spec.rb
deleted file mode 100644
index de8d77e680..0000000000
--- a/Library/Homebrew/test/hardware_spec.rb
+++ /dev/null
@@ -1,87 +0,0 @@
-require "hardware"
-
-module Hardware
-  describe CPU do
-    describe "::type" do
-      it "returns the current CPU's type as a symbol, or :dunno if it cannot be detected" do
-        expect(
-          [
-            :intel,
-            :ppc,
-            :dunno,
-          ],
-        ).to include(described_class.type)
-      end
-    end
-
-    describe "::family" do
-      it "returns the current CPU's family name as a symbol, or :dunno if it cannot be detected" do
-        skip "Needs an Intel CPU." unless described_class.intel?
-
-        expect(
-          [
-            :core,
-            :core2,
-            :penryn,
-            :nehalem,
-            :arrandale,
-            :sandybridge,
-            :ivybridge,
-            :haswell,
-            :broadwell,
-            :skylake,
-            :kabylake,
-            :dunno,
-          ],
-        ).to include(described_class.family)
-      end
-    end
-
-    describe "::can_run?" do
-      it "reports that Intel machines can run Intel executables" do
-        allow(Hardware::CPU).to receive(:type).and_return :intel
-        allow(Hardware::CPU).to receive(:bits).and_return 64
-        expect(Hardware::CPU.can_run?(:i386)).to be true
-        expect(Hardware::CPU.can_run?(:x86_64)).to be true
-      end
-
-      it "reports that PowerPC machines can run PowerPC executables" do
-        allow(Hardware::CPU).to receive(:type).and_return :ppc
-        allow(Hardware::CPU).to receive(:bits).and_return 64
-        expect(Hardware::CPU.can_run?(:ppc)).to be true
-        expect(Hardware::CPU.can_run?(:ppc64)).to be true
-      end
-
-      it "reports that 32-bit Intel machines can't run x86_64 executables" do
-        allow(Hardware::CPU).to receive(:type).and_return :intel
-        allow(Hardware::CPU).to receive(:bits).and_return 32
-        expect(Hardware::CPU.can_run?(:x86_64)).to be false
-      end
-
-      it "reports that 32-bit PowerPC machines can't run ppc64 executables" do
-        allow(Hardware::CPU).to receive(:type).and_return :ppc
-        allow(Hardware::CPU).to receive(:bits).and_return 32
-        expect(Hardware::CPU.can_run?(:ppc64)).to be false
-      end
-
-      it "identifies that Intel and PowerPC machines can't run each others' executables" do
-        allow(Hardware::CPU).to receive(:type).and_return :ppc
-        expect(Hardware::CPU.can_run?(:i386)).to be false
-        expect(Hardware::CPU.can_run?(:x86_64)).to be false
-
-        allow(Hardware::CPU).to receive(:type).and_return :intel
-        expect(Hardware::CPU.can_run?(:ppc)).to be false
-        expect(Hardware::CPU.can_run?(:ppc64)).to be false
-      end
-
-      it "returns false for unknown CPU types" do
-        allow(Hardware::CPU).to receive(:type).and_return :dunno
-        expect(Hardware::CPU.can_run?(:i386)).to be false
-      end
-
-      it "returns false for unknown arches" do
-        expect(Hardware::CPU.can_run?(:blah)).to be false
-      end
-    end
-  end
-end
diff --git a/Library/Homebrew/test/keg_spec.rb b/Library/Homebrew/test/keg_spec.rb
index b2ca62cff9..3c06f5b1c7 100644
--- a/Library/Homebrew/test/keg_spec.rb
+++ b/Library/Homebrew/test/keg_spec.rb
@@ -17,17 +17,6 @@ describe Keg do
     keg
   end
 
-  around do |example|
-    begin
-      @old_stdout = $stdout
-      $stdout = StringIO.new
-
-      example.run
-    ensure
-      $stdout = @old_stdout
-    end
-  end
-
   let(:dst) { HOMEBREW_PREFIX/"bin"/"helloworld" }
   let(:nonexistent) { Pathname.new("/some/nonexistent/path") }
   let(:mode) { OpenStruct.new }
@@ -96,13 +85,15 @@ describe Keg do
       it "only prints what would be done" do
         mode.dry_run = true
 
-        expect(keg.link(mode)).to eq(0)
-        expect(keg).not_to be_linked
+        expect {
+          expect(keg.link(mode)).to eq(0)
+        }.to output(<<~EOF).to_stdout
+          #{HOMEBREW_PREFIX}/bin/goodbye_cruel_world
+          #{HOMEBREW_PREFIX}/bin/helloworld
+          #{HOMEBREW_PREFIX}/bin/hiworld
+        EOF
 
-        ["hiworld", "helloworld", "goodbye_cruel_world"].each do |file|
-          expect($stdout.string).to match("#{HOMEBREW_PREFIX}/bin/#{file}")
-        end
-        expect($stdout.string.lines.count).to eq(3)
+        expect(keg).not_to be_linked
       end
     end
 
@@ -145,10 +136,13 @@ describe Keg do
         mode.overwrite = true
         mode.dry_run = true
 
-        expect(keg.link(mode)).to eq(0)
-        expect(keg).not_to be_linked
+        expect {
+          expect(keg.link(mode)).to eq(0)
+        }.to output(<<~EOF).to_stdout
+          #{dst}
+        EOF
 
-        expect($stdout.string).to eq("#{dst}\n")
+        expect(keg).not_to be_linked
       end
     end
 
diff --git a/Library/Homebrew/test/language_module_requirement_spec.rb b/Library/Homebrew/test/language_module_requirement_spec.rb
deleted file mode 100644
index 43a57ebb59..0000000000
--- a/Library/Homebrew/test/language_module_requirement_spec.rb
+++ /dev/null
@@ -1,46 +0,0 @@
-require "compat/requirements/language_module_requirement"
-
-describe LanguageModuleRequirement, :needs_compat do
-  specify "unique dependencies are not equal" do
-    x = described_class.new(:node, "less")
-    y = described_class.new(:node, "coffee-script")
-    expect(x).not_to eq(y)
-    expect(x.hash).not_to eq(y.hash)
-  end
-
-  context "when module and import name differ" do
-    subject { described_class.new(:python, mod_name, import_name) }
-
-    let(:mod_name) { "foo" }
-    let(:import_name) { "bar" }
-
-    its(:message) { is_expected.to include(mod_name) }
-    its(:the_test) { is_expected.to include("import #{import_name}") }
-  end
-
-  context "when the language is Perl" do
-    it "does not satisfy invalid dependencies" do
-      expect(described_class.new(:perl, "notapackage")).not_to be_satisfied
-    end
-
-    it "satisfies valid dependencies" do
-      expect(described_class.new(:perl, "Env")).to be_satisfied
-    end
-  end
-
-  context "when the language is Python", :needs_python do
-    it "does not satisfy invalid dependencies" do
-      expect(described_class.new(:python, "notapackage")).not_to be_satisfied
-    end
-  end
-
-  context "when the language is Ruby" do
-    it "does not satisfy invalid dependencies" do
-      expect(described_class.new(:ruby, "notapackage")).not_to be_satisfied
-    end
-
-    it "satisfies valid dependencies" do
-      expect(described_class.new(:ruby, "date")).to be_satisfied
-    end
-  end
-end
diff --git a/Library/Homebrew/test/missing_formula_spec.rb b/Library/Homebrew/test/missing_formula_spec.rb
index a9d0083d09..bd17439d2b 100644
--- a/Library/Homebrew/test/missing_formula_spec.rb
+++ b/Library/Homebrew/test/missing_formula_spec.rb
@@ -1,117 +1,85 @@
 require "missing_formula"
 
 describe Homebrew::MissingFormula do
-  context "::reason" do
+  describe "::reason" do
     subject { described_class.reason("gem") }
 
     it { is_expected.not_to be_nil }
   end
 
-  context "::blacklisted_reason" do
-    matcher(:be_blacklisted) do
+  describe "::blacklisted_reason" do
+    matcher :be_blacklisted do
       match do |expected|
         described_class.blacklisted_reason(expected)
       end
     end
 
-    context "rubygems" do
-      %w[gem rubygem rubygems].each do |s|
-        subject { s }
-
-        it { is_expected.to be_blacklisted }
-      end
+    specify "RubyGems is blacklisted" do
+      expect(%w[gem rubygem rubygems]).to all be_blacklisted
     end
 
-    context "latex" do
-      %w[latex tex tex-live texlive TexLive].each do |s|
-        subject { s }
-
-        it { is_expected.to be_blacklisted }
-      end
+    specify "LaTeX is blacklisted" do
+      expect(%w[latex tex tex-live texlive TexLive]).to all be_blacklisted
     end
 
-    context "pip" do
-      subject { "pip" }
-
-      it { is_expected.to be_blacklisted }
+    specify "pip is blacklisted" do
+      expect("pip").to be_blacklisted
     end
 
-    context "pil" do
-      subject { "pil" }
-
-      it { is_expected.to be_blacklisted }
+    specify "PIL is blacklisted" do
+      expect("pil").to be_blacklisted
     end
 
-    context "macruby" do
-      subject { "MacRuby" }
-
-      it { is_expected.to be_blacklisted }
+    specify "MacRuby is blacklisted" do
+      expect("MacRuby").to be_blacklisted
     end
 
-    context "lzma" do
-      %w[lzma liblzma].each do |s|
-        subject { s }
-
-        it { is_expected.to be_blacklisted }
-      end
+    specify "lzma is blacklisted" do
+      expect(%w[lzma liblzma]).to all be_blacklisted
     end
 
-    context "gtest" do
-      %w[gtest googletest google-test].each do |s|
-        subject { s }
-
-        it { is_expected.to be_blacklisted }
-      end
+    specify "gtest is blacklisted" do
+      expect(%w[gtest googletest google-test]).to all be_blacklisted
     end
 
-    context "gmock" do
-      %w[gmock googlemock google-mock].each do |s|
-        subject { s }
-
-        it { is_expected.to be_blacklisted }
-      end
+    specify "gmock is blacklisted" do
+      expect(%w[gmock googlemock google-mock]).to all be_blacklisted
     end
 
-    context "sshpass" do
-      subject { "sshpass" }
-
-      it { is_expected.to be_blacklisted }
+    specify "sshpass is blacklisted" do
+      expect("sshpass").to be_blacklisted
     end
 
-    context "gsutil" do
-      subject { "gsutil" }
-
-      it { is_expected.to be_blacklisted }
+    specify "gsutil is blacklisted" do
+      expect("gsutil").to be_blacklisted
     end
 
-    context "gfortran" do
-      subject { "gfortran" }
-
-      it { is_expected.to be_blacklisted }
+    specify "gfortran is blacklisted" do
+      expect("gfortran").to be_blacklisted
     end
 
-    context "play" do
-      subject { "play" }
-
-      it { is_expected.to be_blacklisted }
+    specify "play is blacklisted" do
+      expect("play").to be_blacklisted
     end
 
-    context "haskell-platform" do
-      subject { "haskell-platform" }
-
-      it { is_expected.to be_blacklisted }
+    specify "haskell-platform is blacklisted" do
+      expect("haskell-platform").to be_blacklisted
     end
 
-    context "xcode", :needs_macos do
-      %w[xcode Xcode].each do |s|
-        subject { s }
+    specify "mysqldump-secure is blacklisted" do
+      expect("mysqldump-secure").to be_blacklisted
+    end
 
-        it { is_expected.to be_blacklisted }
-      end
+    specify "ngrok is blacklisted" do
+      expect("ngrok").to be_blacklisted
+    end
+
+    specify "Xcode is blacklisted", :needs_macos do
+      expect(%w[xcode Xcode]).to all be_blacklisted
     end
   end
 
-  context "::tap_migration_reason" do
+  describe "::tap_migration_reason" do
     subject { described_class.tap_migration_reason(formula) }
 
     before do
@@ -136,7 +104,7 @@ describe Homebrew::MissingFormula do
     end
   end
 
-  context "::deleted_reason" do
+  describe "::deleted_reason" do
     subject { described_class.deleted_reason(formula, silent: true) }
 
     before do
diff --git a/Library/Homebrew/test/os/linux/osxfuse_requirement_spec.rb b/Library/Homebrew/test/os/linux/osxfuse_requirement_spec.rb
deleted file mode 100644
index c45af2fa79..0000000000
--- a/Library/Homebrew/test/os/linux/osxfuse_requirement_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require "requirements/osxfuse_requirement"
-
-describe OsxfuseRequirement do
-  subject { described_class.new([]) }
-
-  describe "#message" do
-    its(:message) { is_expected.to match("libfuse is required to install this formula") }
-  end
-end
diff --git a/Library/Homebrew/test/os/mac/diagnostic_spec.rb b/Library/Homebrew/test/os/mac/diagnostic_spec.rb
index f04652a936..ffa4ebca9e 100644
--- a/Library/Homebrew/test/os/mac/diagnostic_spec.rb
+++ b/Library/Homebrew/test/os/mac/diagnostic_spec.rb
@@ -22,14 +22,14 @@ describe Homebrew::Diagnostic::Checks do
       .to match("The following beta release of XQuartz is installed: 2.7.10_beta2")
   end
 
-  specify "#check_xcode_8_without_clt_on_el_capitan" do
+  specify "#check_if_xcode_needs_clt_installed" do
     allow(MacOS).to receive(:version).and_return(OS::Mac::Version.new("10.11"))
     allow(MacOS::Xcode).to receive(:installed?).and_return(true)
     allow(MacOS::Xcode).to receive(:version).and_return("8.0")
     allow(MacOS::Xcode).to receive(:without_clt?).and_return(true)
 
-    expect(subject.check_xcode_8_without_clt_on_el_capitan)
-      .to match("You have Xcode 8 installed without the CLT")
+    expect(subject.check_if_xcode_needs_clt_installed)
+      .to match("Xcode alone is not sufficient on El Capitan")
   end
 
   specify "#check_homebrew_prefix" do
diff --git a/Library/Homebrew/test/os/mac/osxfuse_requirement_spec.rb b/Library/Homebrew/test/os/mac/osxfuse_requirement_spec.rb
deleted file mode 100644
index 06d3d885e6..0000000000
--- a/Library/Homebrew/test/os/mac/osxfuse_requirement_spec.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-require "requirements/osxfuse_requirement"
-
-describe OsxfuseRequirement do
-  subject { described_class.new([]) }
-
-  describe "::binary_osxfuse_installed?" do
-    it "returns false if fuse.h does not exist" do
-      allow(File).to receive(:exist?).and_return(false)
-      expect(described_class).not_to be_binary_osxfuse_installed
-    end
-
-    it "returns false if osxfuse include directory is a symlink" do
-      allow(File).to receive(:exist?).and_return(true)
-      allow(File).to receive(:symlink?).and_return(true)
-      expect(described_class).not_to be_binary_osxfuse_installed
-    end
-  end
-
-  describe "environment" do
-    it "adds the fuse directories to the appropriate paths" do
-      expect(ENV).to receive(:append_path).with("PKG_CONFIG_PATH", any_args)
-      expect(ENV).to receive(:append_path).with("HOMEBREW_LIBRARY_PATHS", any_args)
-      expect(ENV).to receive(:append_path).with("HOMEBREW_INCLUDE_PATHS", any_args)
-      subject.modify_build_environment
-    end
-  end
-end
-
-describe NonBinaryOsxfuseRequirement do
-  subject { described_class.new([]) }
-
-  describe "#message" do
-    msg = /osxfuse is already installed from the binary distribution/
-    its(:message) { is_expected.to match(msg) }
-  end
-end
diff --git a/Library/Homebrew/test/os_requirement_spec.rb b/Library/Homebrew/test/os_requirement_spec.rb
deleted file mode 100644
index 87f86231c1..0000000000
--- a/Library/Homebrew/test/os_requirement_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require "requirements/linux_requirement"
-require "requirements/macos_requirement"
-
-describe LinuxRequirement do
-  describe "#satisfied?" do
-    it "returns true if OS is Linux" do
-      expect(subject.satisfied?).to eq(OS.linux?)
-    end
-  end
-end
-
-describe MacOSRequirement do
-  describe "#satisfied?" do
-    it "returns true if OS is macOS" do
-      expect(subject.satisfied?).to eq(OS.mac?)
-    end
-  end
-end
diff --git a/Library/Homebrew/test/pathname_spec.rb b/Library/Homebrew/test/pathname_spec.rb
index ac568d27fb..090897f6a3 100644
--- a/Library/Homebrew/test/pathname_spec.rb
+++ b/Library/Homebrew/test/pathname_spec.rb
@@ -1,4 +1,3 @@
-require "tmpdir"
 require "extend/pathname"
 require "install_renamed"
 
diff --git a/Library/Homebrew/test/requirements/linux_requirement_spec.rb b/Library/Homebrew/test/requirements/linux_requirement_spec.rb
new file mode 100644
index 0000000000..3d456f1f1f
--- /dev/null
+++ b/Library/Homebrew/test/requirements/linux_requirement_spec.rb
@@ -0,0 +1,11 @@
+require "requirements/linux_requirement"
+
+describe LinuxRequirement do
+  subject(:requirement) { described_class.new }
+
+  describe "#satisfied?" do
+    it "returns true on Linux" do
+      expect(requirement.satisfied?).to eq(OS.linux?)
+    end
+  end
+end
diff --git a/Library/Homebrew/test/requirements/macos_requirement_spec.rb b/Library/Homebrew/test/requirements/macos_requirement_spec.rb
new file mode 100644
index 0000000000..7828e73185
--- /dev/null
+++ b/Library/Homebrew/test/requirements/macos_requirement_spec.rb
@@ -0,0 +1,11 @@
+require "requirements/macos_requirement"
+
+describe MacOSRequirement do
+  subject(:requirement) { described_class.new }
+
+  describe "#satisfied?" do
+    it "returns true on macOS" do
+      expect(requirement.satisfied?).to eq(OS.mac?)
+    end
+  end
+end
diff --git a/Library/Homebrew/test/requirements/non_binary_osxfuse_requirement_spec.rb b/Library/Homebrew/test/requirements/non_binary_osxfuse_requirement_spec.rb
new file mode 100644
index 0000000000..84fb448740
--- /dev/null
+++ b/Library/Homebrew/test/requirements/non_binary_osxfuse_requirement_spec.rb
@@ -0,0 +1,9 @@
+require "requirements/non_binary_osxfuse_requirement"
+
+describe NonBinaryOsxfuseRequirement, :needs_macos do
+  subject { described_class.new([]) }
+
+  describe "#message" do
+    its(:message) { is_expected.to match("osxfuse is already installed from the binary distribution") }
+  end
+end
diff --git a/Library/Homebrew/test/requirements/osxfuse_requirement_spec.rb b/Library/Homebrew/test/requirements/osxfuse_requirement_spec.rb
new file mode 100644
index 0000000000..59a3553077
--- /dev/null
+++ b/Library/Homebrew/test/requirements/osxfuse_requirement_spec.rb
@@ -0,0 +1,50 @@
+require "requirements/osxfuse_requirement"
+
+describe OsxfuseRequirement do
+  subject(:requirement) { described_class.new([]) }
+
+  describe "::binary_osxfuse_installed?", :needs_macos do
+    alias_matcher :have_binary_osxfuse_installed, :be_binary_osxfuse_installed
+
+    it "returns false if fuse.h does not exist" do
+      allow(File).to receive(:exist?).and_return(false)
+      expect(described_class).not_to have_binary_osxfuse_installed
+    end
+
+    it "returns false if osxfuse include directory is a symlink" do
+      allow(File).to receive(:exist?).and_return(true)
+      allow(File).to receive(:symlink?).and_return(true)
+      expect(described_class).not_to have_binary_osxfuse_installed
+    end
+  end
+
+  describe "#modify_build_environment", :needs_macos do
+    it "adds the fuse directories to PKG_CONFIG_PATH" do
+      allow(ENV).to receive(:append_path)
+      requirement.modify_build_environment
+      expect(ENV).to have_received(:append_path).with("PKG_CONFIG_PATH", any_args)
+    end
+
+    it "adds the fuse directories to HOMEBREW_LIBRARY_PATHS" do
+      allow(ENV).to receive(:append_path)
+      requirement.modify_build_environment
+      expect(ENV).to have_received(:append_path).with("HOMEBREW_LIBRARY_PATHS", any_args)
+    end
+
+    it "adds the fuse directories to HOMEBREW_INCLUDE_PATHS" do
+      allow(ENV).to receive(:append_path)
+      requirement.modify_build_environment
+      expect(ENV).to have_received(:append_path).with("HOMEBREW_INCLUDE_PATHS", any_args)
+    end
+  end
+
+  describe "#message" do
+    it "prompts for installation of 'libfuse' on Linux", :needs_linux do
+      expect(requirement.message).to match("libfuse is required to install this formula")
+    end
+
+    it "prompts for installation of 'osxFuse' on macOS", :needs_macos do
+      expect(requirement.message).to match("osxfuse.github.io")
+    end
+  end
+end
diff --git a/Library/Homebrew/test/rubocops/components_order_cop_spec.rb b/Library/Homebrew/test/rubocops/components_order_cop_spec.rb
index cd7cc5893a..7466f2d6b6 100644
--- a/Library/Homebrew/test/rubocops/components_order_cop_spec.rb
+++ b/Library/Homebrew/test/rubocops/components_order_cop_spec.rb
@@ -1,6 +1,6 @@
 require_relative "../../rubocops/components_order_cop"
 
-describe RuboCop::Cop::FormulaAuditStrict::ComponentsOrder do
+describe RuboCop::Cop::FormulaAudit::ComponentsOrder do
   subject(:cop) { described_class.new }
 
   context "When auditing formula components order" do
diff --git a/Library/Homebrew/test/rubocops/components_redundancy_cop_spec.rb b/Library/Homebrew/test/rubocops/components_redundancy_cop_spec.rb
index d8878ae797..fd325e5846 100644
--- a/Library/Homebrew/test/rubocops/components_redundancy_cop_spec.rb
+++ b/Library/Homebrew/test/rubocops/components_redundancy_cop_spec.rb
@@ -1,6 +1,6 @@
 require_relative "../../rubocops/components_redundancy_cop"
 
-describe RuboCop::Cop::FormulaAuditStrict::ComponentsRedundancy do
+describe RuboCop::Cop::FormulaAudit::ComponentsRedundancy do
   subject(:cop) { described_class.new }
 
   context "When auditing formula components common errors" do
diff --git a/Library/Homebrew/test/rubocops/urls_cop_spec.rb b/Library/Homebrew/test/rubocops/urls_cop_spec.rb
index 494028bd50..9f9f6ded1e 100644
--- a/Library/Homebrew/test/rubocops/urls_cop_spec.rb
+++ b/Library/Homebrew/test/rubocops/urls_cop_spec.rb
@@ -164,7 +164,7 @@ describe RuboCop::Cop::FormulaAudit::Urls do
   end
 end
 
-describe RuboCop::Cop::FormulaAuditStrict::PyPiUrls do
+describe RuboCop::Cop::FormulaAudit::PyPiUrls do
   subject(:cop) { described_class.new }
 
   context "when a pypi.python.org URL is used" do
diff --git a/Library/Homebrew/test/spec_helper.rb b/Library/Homebrew/test/spec_helper.rb
index cba530736a..2ad3b2e642 100644
--- a/Library/Homebrew/test/spec_helper.rb
+++ b/Library/Homebrew/test/spec_helper.rb
@@ -1,13 +1,3 @@
-require "find"
-require "pathname"
-require "rspec/its"
-require "rspec/wait"
-require "rspec/retry"
-require "rubocop"
-require "rubocop/rspec/support"
-require "set"
-require "support/no_seed_progress_formatter"
-
 if ENV["HOMEBREW_TESTS_COVERAGE"]
   require "simplecov"
 
@@ -17,12 +7,19 @@ if ENV["HOMEBREW_TESTS_COVERAGE"]
   end
 end
 
+require "rspec/its"
+require "rspec/wait"
+require "rspec/retry"
+require "rubocop"
+require "rubocop/rspec/support"
+require "find"
+
 $LOAD_PATH.unshift(File.expand_path("#{ENV["HOMEBREW_LIBRARY"]}/Homebrew"))
 $LOAD_PATH.unshift(File.expand_path("#{ENV["HOMEBREW_LIBRARY"]}/Homebrew/test/support/lib"))
 
 require "global"
-require "tap"
 
+require "test/support/no_seed_progress_formatter"
 require "test/support/helper/fixtures"
 require "test/support/helper/formula"
 require "test/support/helper/mktmpdir"
@@ -133,6 +130,7 @@ RSpec.configure do |config|
         HOMEBREW_LIBRARY/"Taps/homebrew/homebrew-foo",
         HOMEBREW_LIBRARY/"Taps/homebrew/homebrew-services",
         HOMEBREW_LIBRARY/"Taps/homebrew/homebrew-shallow",
+        HOMEBREW_LIBRARY/"PinnedTaps",
         HOMEBREW_REPOSITORY/".git",
         CoreTap.instance.path/".git",
         CoreTap.instance.alias_dir,
diff --git a/Library/Homebrew/test/support/fixtures/cask/Casks/with-dsl-version.rb b/Library/Homebrew/test/support/fixtures/cask/Casks/compat/with-dsl-version.rb
similarity index 100%
rename from Library/Homebrew/test/support/fixtures/cask/Casks/with-dsl-version.rb
rename to Library/Homebrew/test/support/fixtures/cask/Casks/compat/with-dsl-version.rb
diff --git a/Library/Homebrew/test/support/fixtures/cask/Casks/generic-artifact-no-target.rb b/Library/Homebrew/test/support/fixtures/cask/Casks/generic-artifact-no-target.rb
deleted file mode 100644
index a3e65caab2..0000000000
--- a/Library/Homebrew/test/support/fixtures/cask/Casks/generic-artifact-no-target.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-cask 'generic-artifact-no-target' do
-  artifact 'Caffeine.app'
-end
diff --git a/Library/Homebrew/test/support/fixtures/cask/Casks/with-generic-artifact-no-target.rb b/Library/Homebrew/test/support/fixtures/cask/Casks/invalid/invalid-generic-artifact-no-target.rb
similarity index 83%
rename from Library/Homebrew/test/support/fixtures/cask/Casks/with-generic-artifact-no-target.rb
rename to Library/Homebrew/test/support/fixtures/cask/Casks/invalid/invalid-generic-artifact-no-target.rb
index f7f1ddc221..b806a94fca 100644
--- a/Library/Homebrew/test/support/fixtures/cask/Casks/with-generic-artifact-no-target.rb
+++ b/Library/Homebrew/test/support/fixtures/cask/Casks/invalid/invalid-generic-artifact-no-target.rb
@@ -1,4 +1,4 @@
-cask 'with-generic-artifact-no-target' do
+cask 'invalid-generic-artifact-no-target' do
   version '1.2.3'
   sha256 '67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94'
 
diff --git a/Library/Homebrew/test/support/fixtures/cask/Casks/with-two-apps-incorrect.rb b/Library/Homebrew/test/support/fixtures/cask/Casks/with-two-apps-incorrect.rb
deleted file mode 100644
index c3ca473bda..0000000000
--- a/Library/Homebrew/test/support/fixtures/cask/Casks/with-two-apps-incorrect.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-cask 'with-two-apps-incorrect' do
-  version '1.2.3'
-  sha256 '67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94'
-
-  url "file://#{TEST_FIXTURE_DIR}/cask/caffeine.zip"
-  homepage 'http://example.com/local-caffeine'
-
-  app 'Caffeine.app', 'Caffeine.app/Contents/MacOS/Caffeine'
-end
diff --git a/Library/Homebrew/test/support/lib/config.rb b/Library/Homebrew/test/support/lib/config.rb
index a59d80c995..7408b3e34a 100644
--- a/Library/Homebrew/test/support/lib/config.rb
+++ b/Library/Homebrew/test/support/lib/config.rb
@@ -2,9 +2,6 @@ unless ENV["HOMEBREW_BREW_FILE"]
   raise "HOMEBREW_BREW_FILE was not exported! Please call bin/brew directly!"
 end
 
-require "constants"
-
-require "tmpdir"
 require "pathname"
 
 HOMEBREW_BREW_FILE = Pathname.new(ENV["HOMEBREW_BREW_FILE"])
diff --git a/Library/Homebrew/test/tap_spec.rb b/Library/Homebrew/test/tap_spec.rb
index 5e82370aac..fafc8a49af 100644
--- a/Library/Homebrew/test/tap_spec.rb
+++ b/Library/Homebrew/test/tap_spec.rb
@@ -209,6 +209,31 @@ describe Tap do
       expect { already_tapped_tap.install full_clone: true }.to raise_error(TapAlreadyUnshallowError)
     end
 
+    describe "force_auto_update" do
+      before do
+        setup_git_repo
+      end
+
+      let(:already_tapped_tap) { described_class.new("Homebrew", "foo") }
+
+      it "defaults to nil" do
+        expect(already_tapped_tap).to be_installed
+        expect(already_tapped_tap.config["forceautoupdate"]).to be_nil
+      end
+
+      it "enables forced auto-updates when true" do
+        expect(already_tapped_tap).to be_installed
+        already_tapped_tap.install force_auto_update: true
+        expect(already_tapped_tap.config["forceautoupdate"]).to eq("true")
+      end
+
+      it "disables forced auto-updates when false" do
+        expect(already_tapped_tap).to be_installed
+        already_tapped_tap.install force_auto_update: false
+        expect(already_tapped_tap.config["forceautoupdate"]).to eq("false")
+      end
+    end
+
     specify "Git error" do
       tap = described_class.new("user", "repo")
 
diff --git a/Library/Homebrew/test/utils/curl_spec.rb b/Library/Homebrew/test/utils/curl_spec.rb
new file mode 100644
index 0000000000..a843a2f2de
--- /dev/null
+++ b/Library/Homebrew/test/utils/curl_spec.rb
@@ -0,0 +1,15 @@
+require "utils/curl"
+
+describe "curl" do
+  describe "curl_args" do
+    it "returns -q as the first argument when HOMEBREW_CURLRC is not set" do
+      # -q must be the first argument according to "man curl"
+      expect(curl_args("foo")[1]).to eq("-q")
+    end
+
+    it "doesn't return -q as the first argument when HOMEBREW_CURLRC is set" do
+      ENV["HOMEBREW_CURLRC"] = "1"
+      expect(curl_args("foo")[1]).to_not eq("-q")
+    end
+  end
+end
diff --git a/Library/Homebrew/test/utils/tty_spec.rb b/Library/Homebrew/test/utils/tty_spec.rb
index e4b61a61ca..4489b818a9 100644
--- a/Library/Homebrew/test/utils/tty_spec.rb
+++ b/Library/Homebrew/test/utils/tty_spec.rb
@@ -1,4 +1,3 @@
-require "utils"
 
 describe Tty do
   describe "::strip_ansi" do
diff --git a/Library/Homebrew/test/utils_spec.rb b/Library/Homebrew/test/utils_spec.rb
index 21fcc3249f..dbfd1c3859 100644
--- a/Library/Homebrew/test/utils_spec.rb
+++ b/Library/Homebrew/test/utils_spec.rb
@@ -1,4 +1,3 @@
-require "utils"
 
 describe "globally-scoped helper methods" do
   let(:dir) { mktmpdir }
diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index dcc69ecb30..84eb8aa8cc 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -1,6 +1,4 @@
-require "pathname"
 require "emoji"
-require "exceptions"
 require "utils/analytics"
 require "utils/curl"
 require "utils/fork"
diff --git a/Library/Homebrew/utils/curl.rb b/Library/Homebrew/utils/curl.rb
index 7b2488ec72..216c2bf81e 100644
--- a/Library/Homebrew/utils/curl.rb
+++ b/Library/Homebrew/utils/curl.rb
@@ -1,4 +1,3 @@
-require "pathname"
 require "open3"
 
 def curl_executable
@@ -12,10 +11,12 @@ def curl_executable
 end
 
 def curl_args(*extra_args, show_output: false, user_agent: :default)
-  args = [
-    curl_executable.to_s,
-    "--show-error",
-  ]
+  args = [curl_executable.to_s]
+
+  # do not load .curlrc unless requested (must be the first argument)
+  args << "-q" unless ENV["HOMEBREW_CURLRC"]
+
+  args << "--show-error"
 
   args << "--user-agent" << case user_agent
   when :browser, :fake
diff --git a/Library/Homebrew/utils/github.rb b/Library/Homebrew/utils/github.rb
index b6a27b3283..e69e37cc5e 100644
--- a/Library/Homebrew/utils/github.rb
+++ b/Library/Homebrew/utils/github.rb
@@ -7,8 +7,8 @@ module GitHub
   API_URL = "https://api.github.com".freeze
 
   CREATE_GIST_SCOPES = ["gist"].freeze
-  CREATE_ISSUE_SCOPES = ["public_repo"].freeze
-  ALL_SCOPES = (CREATE_GIST_SCOPES + CREATE_ISSUE_SCOPES).freeze
+  CREATE_ISSUE_FORK_OR_PR_SCOPES = ["public_repo"].freeze
+  ALL_SCOPES = (CREATE_GIST_SCOPES + CREATE_ISSUE_FORK_OR_PR_SCOPES).freeze
   ALL_SCOPES_URL = Formatter.url("https://github.com/settings/tokens/new?scopes=#{ALL_SCOPES.join(",")}&description=Homebrew").freeze
 
   Error = Class.new(RuntimeError)
@@ -253,6 +253,20 @@ module GitHub
     prs.each { |i| puts "#{i["title"]} (#{i["html_url"]})" }
   end
 
+  def create_fork(repo)
+    url = "https://api.github.com/repos/#{repo}/forks"
+    data = {}
+    scopes = CREATE_ISSUE_FORK_OR_PR_SCOPES
+    open_api(url, data: data, scopes: scopes)
+  end
+
+  def create_pull_request(repo, title, head, base, body)
+    url = "https://api.github.com/repos/#{repo}/pulls"
+    data = { title: title, head: head, base: base, body: body }
+    scopes = CREATE_ISSUE_FORK_OR_PR_SCOPES
+    open_api(url, data: data, scopes: scopes)
+  end
+
   def private_repo?(full_name)
     uri = url_to "repos", full_name
     open_api(uri) { |json| json["private"] }
diff --git a/README.md b/README.md
index 240774ed2e..d9bc5dc48c 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ Second, read the [Troubleshooting Checklist](https://docs.brew.sh/Troubleshootin
 [![Travis](https://img.shields.io/travis/Homebrew/brew.svg)](https://travis-ci.org/Homebrew/brew)
 [![Codecov](https://img.shields.io/codecov/c/github/Homebrew/brew.svg)](https://codecov.io/gh/Homebrew/brew)
 
-We'd love you to contribute to Homebrew. First, please read our [Contribution Guide](https://github.com/Homebrew/brew/blob/master/CONTRIBUTING.md) and [Code of Conduct](https://github.com/Homebrew/brew/blob/master/CODE_OF_CONDUCT.md#code-of-conduct).
+We'd love you to contribute to Homebrew. First, please read our [Contribution Guide](CONTRIBUTING.md) and [Code of Conduct](CODE_OF_CONDUCT.md#code-of-conduct).
 
 We explicitly welcome contributions from people who have never contributed to open-source before: we were all beginners once! We can help build on a partially working pull request with the aim of getting it merged. We are also actively seeking to diversify our contributors and especially welcome contributions from women from all backgrounds and people of colour.
 
@@ -52,7 +52,7 @@ Former maintainers with significant contributions include [Tim Smith](https://gi
 - [@MacHomebrew (Twitter)](https://twitter.com/MacHomebrew)
 
 ## License
-Code is under the [BSD 2-clause "Simplified" License](https://github.com/Homebrew/brew/tree/master/LICENSE.txt).
+Code is under the [BSD 2-clause "Simplified" License](LICENSE.txt).
 Documentation is under the [Creative Commons Attribution license](https://creativecommons.org/licenses/by/4.0/).
 
 ## Donations
diff --git a/completions/bash/brew b/completions/bash/brew
index 02c862bbdd..406b6a901f 100644
--- a/completions/bash/brew
+++ b/completions/bash/brew
@@ -430,11 +430,10 @@ _brew_tap() {
   local cur="${COMP_WORDS[COMP_CWORD]}"
   case "$cur" in
     --*)
-      __brewcomp "--repair --list-official --list-pinned"
+      __brewcomp "--repair --list-pinned"
       return
       ;;
   esac
-  __brewcomp "$(brew tap --list-official)"
 }
 
 _brew_tap_info() {
@@ -716,7 +715,7 @@ _brew_cask_upgrade ()
         return
         ;;
     esac
-    __brew_cask_complete_outdated    
+    __brew_cask_complete_outdated
 }
 
 _brew_cask ()
diff --git a/completions/zsh/_brew b/completions/zsh/_brew
index e4f874bfb6..45f50ccb02 100644
--- a/completions/zsh/_brew
+++ b/completions/zsh/_brew
@@ -56,12 +56,6 @@ __brew_installed_taps() {
   _describe -t installed-taps 'installed taps' taps
 }
 
-__brew_official_taps() {
-  local -a taps
-  taps=($(brew tap --list-official))
-  _describe -t official-taps 'official taps' taps
-}
-
 __brew_pinned_taps() {
   local -a taps
   taps=($(brew tap --list-pinned))
@@ -70,8 +64,7 @@ __brew_pinned_taps() {
 
 __brew_any_tap() {
   _alternative \
-    'installed-taps:installed taps:__brew_installed_taps' \
-    'official-taps:official taps:__brew_official_taps'
+    'installed-taps:installed taps:__brew_installed_taps'
 }
 
 __brew_common_commands() {
@@ -605,19 +598,15 @@ _brew_switch() {
 # brew tap:
 # brew tap [--full] user/repo [URL]:
 # brew tap --repair:
-# brew tap --list-official:
 # brew tap --list-pinned:
 _brew_tap() {
   _arguments \
     - empty-args \
     - repo-args \
       '(--full)--full[perform a full clone]' \
-      ':repo:__brew_official_taps' \
       '::url:_urls' \
     - repair-args \
       '(--repair)--repair' \
-    - list-official \
-      '(--list-official)--list-official[list all official taps]' \
     - list-pinned \
       '(--list-pinned)--list-pinned[list all pinned taps]'
 }
diff --git a/docs/Analytics.md b/docs/Analytics.md
index 18dc7bfa62..2ffff86444 100644
--- a/docs/Analytics.md
+++ b/docs/Analytics.md
@@ -8,6 +8,9 @@ Homebrew is provided free of charge and run entirely by volunteers in their spar
 - If a formula is widely used and is failing often it will enable us to prioritise fixing that formula over others.
 - Collecting the OS version allows us to decide what versions of macOS to prioritise and support and identify build failures that occur only on single versions.
 
+## How Long?
+Homebrew's anonymous user and event data have a 14 month retention period. This is the [lowest possible value for Google Analytics](https://support.google.com/analytics/answer/7667196).
+
 ## What?
 Homebrew's analytics record some shared information for every event:
 
diff --git a/docs/FAQ.md b/docs/FAQ.md
index 9d76bf4ab6..fdbbb7eb0c 100644
--- a/docs/FAQ.md
+++ b/docs/FAQ.md
@@ -26,7 +26,7 @@ To allow that formulae to update again:
 
     brew unpin <formula>
 
-Note that pinned, outdated formulae that are depended on by another formula will be upgraded when required as we do not allow formulae to be built against non-latest versions.
+Note that pinned, outdated formulae that are depended on by another formula need to be upgraded when required as we do not allow formulae to be built against non-latest versions.
 
 ## How do I uninstall old versions of a formula?
 By default, Homebrew does not uninstall old versions of a formula, so
@@ -55,7 +55,7 @@ and run `./uninstall --help` to view more uninstall options.
 ## How do I uninstall a formula?
 If you do not uninstall all of the versions that Homebrew has installed,
 Homebrew will continue to attempt to install the newest version it knows
-about when you run `brew upgrade --all`. This can be surprising.
+about when you run `brew upgrade`. This can be surprising.
 
 To remove a formula entirely, you may run `brew uninstall formula_name --force`.
 
@@ -125,9 +125,9 @@ Or:
     fix this for Homebrew formulae (although we don’t always test for
     it), but you’ll find that many RubyGems and Python setup scripts
     break which is something outside our control.
-3.  **It’s safe**<br>Apple has left this directory for us. Which means
-    there is no `/usr/local` directory by default, so there
-    is no need to worry about messing up existing tools.
+3.  **It’s safe**<br>Apple has assigned this directory for non-system utilities. Which means
+    there is no files in `/usr/local` by default, so there
+    is no need to worry about messing up existing or system tools.
 
 **If you plan to install gems that depend on
 brews then save yourself a bunch of hassle and install to
@@ -139,21 +139,16 @@ It is not always straightforward to tell `gem` to look in non-standard directori
 **tl;dr** Sudo is dangerous, and you installed TextMate.app without sudo
 anyway.
 
-Homebrew is designed to work without using sudo. You can decide to use
-it but we strongly recommend not to do so. If you have used sudo and run
-into a bug then this is likely to be the cause. Please don’t file a bug
-report unless you can reproduce it after reinstalling Homebrew from
-scratch without using sudo.
+Homebrew refuses to work using sudo.
 
-You should only ever sudo a tool you trust. Of course, you can trust
-Homebrew ;) But do you trust the multi-megabyte Makefile that Homebrew
-runs? Developers often understand C++ far better than they understand
-make syntax. It’s too high a risk to sudo such stuff. It could break
-your base system, or alter it subtly.
+You should only ever sudo a tool you trust. Of course, you can trust Homebrew
+;) But do you trust the multi-megabyte Makefile that Homebrew runs? Developers
+often understand C++ far better than they understand make syntax. It’s too high
+a risk to sudo such stuff. It could modify (or upload) any files on your
+system.And indeed, we’ve seen some build scripts try to modify `/usr` even when
+the prefix was specified as something else entirely.
 
-And indeed, we’ve seen some build scripts try to modify
-`/usr` even when the prefix was specified as something else
-entirely.
+We use the macOS sandbox to stop this but this doesn't work when run as the `root` user (which also has read and write access to almost everything on the system).
 
 Did you `chown root /Applications/TextMate.app`? Probably
 not. So is it that important to `chown root wget`?
diff --git a/docs/Formula-Cookbook.md b/docs/Formula-Cookbook.md
index 3f6902409a..37237265d7 100644
--- a/docs/Formula-Cookbook.md
+++ b/docs/Formula-Cookbook.md
@@ -31,7 +31,6 @@ Before submitting a new formula make sure your package:
 
 *   meets all our [Acceptable Formulae](Acceptable-Formulae.md) requirements
 *   isn't already in Homebrew (check `brew search <formula>`)
-*   isn't in another official [Homebrew tap](https://github.com/Homebrew)
 *   isn't already waiting to be merged (check the [issue tracker](https://github.com/Homebrew/homebrew-core/pulls))
 *   is still supported by upstream (i.e. doesn't require extensive patching)
 *   has a stable, tagged version (i.e. not just a GitHub repository with no versions)
diff --git a/docs/How-To-Open-a-Homebrew-Pull-Request.md b/docs/How-To-Open-a-Homebrew-Pull-Request.md
index 812d990e08..16b1234940 100644
--- a/docs/How-To-Open-a-Homebrew-Pull-Request.md
+++ b/docs/How-To-Open-a-Homebrew-Pull-Request.md
@@ -25,8 +25,6 @@ Depending on the change you want to make, you need to send the pull request to t
 3. Add your pushable forked repository with `git remote add <YOUR_USERNAME> https://github.com/<YOUR_USERNAME>/homebrew-core.git`
   * `<YOUR_USERNAME>` is your GitHub username, not your local machine username.
 
-For formulae in central taps other than `homebrew/core`, such as `homebrew/php`, substitute that tap's name for `homebrew/core` in each step, and alter the GitHub repository URLs as necessary.
-
 ## Create your pull request from a new branch
 
 To make a new branch and submit it for review, create a GitHub pull request with the following steps:
diff --git a/docs/How-to-Create-and-Maintain-a-Tap.md b/docs/How-to-Create-and-Maintain-a-Tap.md
index 610380aa60..76b0bbda67 100644
--- a/docs/How-to-Create-and-Maintain-a-Tap.md
+++ b/docs/How-to-Create-and-Maintain-a-Tap.md
@@ -16,7 +16,7 @@ repository’s root, or under `Formula` or `HomebrewFormula` subdirectories. We
 recommend the latter options because it makes the repository organisation
 easier to grasp, and top-level files are not mixed with formulae.
 
-See [homebrew/php](https://github.com/Homebrew/homebrew-php) for an example of
+See [homebrew/core](https://github.com/Homebrew/homebrew-core) for an example of
 a tap with a `Formula` subdirectory.
 
 ### Installing
diff --git a/docs/Installation.md b/docs/Installation.md
index 9f091d2e58..f186b546e1 100644
--- a/docs/Installation.md
+++ b/docs/Installation.md
@@ -11,7 +11,7 @@ it does it too. And you have to confirm everything it will do before it starts.
 
 ## Requirements
 * An Intel CPU <sup>[1](#1)</sup>
-* OS X 10.10 or higher <sup>[2](#2)</sup>
+* OS X 10.11 or higher <sup>[2](#2)</sup>
 * Command Line Tools (CLT) for Xcode: `xcode-select --install`,
   [developer.apple.com/downloads](https://developer.apple.com/downloads) or
   [Xcode](https://itunes.apple.com/us/app/xcode/id497799835) <sup>[3](#3)</sup>
@@ -19,11 +19,16 @@ it does it too. And you have to confirm everything it will do before it starts.
 
 ## Alternative Installs
 
+### OS X Lion 10.7 and below
+
+Using the instructions on https://brew.sh or below whenever you call `curl` you must pass `--insecure` as an argument. This is because your system `curl` is too old to speak to GitHub using HTTPS. Don't worry, on the first `brew update` Homebrew will install a newer, more secure `curl` for your machine.
+
 ### Untar anywhere
 Just extract (or `git clone`) Homebrew wherever you want. Just
 avoid:
 
 * Directories with names that contain spaces. Homebrew itself can handle spaces, but many build scripts cannot.
+* `/tmp` subdirectories because Homebrew gets upset
 * `/sw` and `/opt/local` because build scripts get confused when Homebrew is there instead of Fink or MacPorts, respectively.
 
 However do yourself a favor and install to `/usr/local`. Some things may
@@ -46,7 +51,7 @@ you can assume you will have trouble if you don’t conform. Also, you can find
 PowerPC and Tiger branches from other users in the fork network. See
 [Interesting Taps and Forks](Interesting-Taps-and-Forks.md).
 
-<a name="2"><sup>2</sup></a> 10.10 or higher is recommended. 10.5–10.9 are
+<a name="2"><sup>2</sup></a> 10.11 or higher is recommended. 10.5–10.10 are
 supported on a best-effort basis. For 10.4 see
 [Tigerbrew](https://github.com/mistydemeo/tigerbrew).
 
diff --git a/docs/Interesting-Taps-and-Forks.md b/docs/Interesting-Taps-and-Forks.md
index 4d569e6c05..57f0730b72 100644
--- a/docs/Interesting-Taps-and-Forks.md
+++ b/docs/Interesting-Taps-and-Forks.md
@@ -3,15 +3,9 @@
 A _tap_ is homebrew-speak for a Git repository containing extra formulae.
 Homebrew has the capability to add (and remove) multiple taps to your local installation with the `brew tap` and `brew untap` commands. Type `man brew` in your Terminal. The main repository [https://github.com/Homebrew/homebrew-core](https://github.com/Homebrew/homebrew-core), often called `homebrew/core`, is always built-in.
 
-## Main taps
+Your taps are Git repositories located at `$(brew --repository)/Library/Taps`.
 
-*   [homebrew/php](https://github.com/Homebrew/homebrew-php): Repository for PHP-related formulae.
-
-`brew search` looks in these taps as well as in [homebrew/core](https://github.com/Homebrew/homebrew-core) so don't worry about missing stuff.
-
-You can be added as a maintainer for one of the Homebrew organization taps and aid the project! If you are interested please feel free to ask in an issue or pull request after submitting multiple high-quality pull requests. We want your help!
-
-## Other interesting taps
+## Unsupported interesting taps
 
 *   [denji/nginx](https://github.com/denji/homebrew-nginx): A tap for NGINX modules, intended for its `nginx-full` formula which includes more module options.
 
@@ -37,12 +31,8 @@ You can be added as a maintainer for one of the Homebrew organization taps and a
 
 *   [lifepillar/appleii](https://github.com/lifepillar/homebrew-appleii): Formulae for vintage Apple emulation.
 
-## Interesting forks
+## Unsupported interesting forks
 
 *   [mistydemeo/tigerbrew](https://github.com/mistydemeo/tigerbrew): Experimental Tiger PowerPC version.
 
 *   [Linuxbrew/brew](https://github.com/Linuxbrew/brew): Experimental Linux version.
-
-## Technical details
-
-Your taps are Git repositories located at `$(brew --repository)/Library/Taps`.
diff --git a/docs/Maintainer-Guidelines.md b/docs/Maintainer-Guidelines.md
index 1d69f53811..34d046a4bb 100644
--- a/docs/Maintainer-Guidelines.md
+++ b/docs/Maintainer-Guidelines.md
@@ -104,3 +104,14 @@ Whitespace corrections (to Ruby standard etc.) are allowed (in fact this
 is a good opportunity to do it) provided the line itself has some kind
 of modification that is not whitespace in it. But be careful about
 making changes to inline patches—make sure they still apply.
+
+## Communication
+Maintainers have a variety of ways to communicate with each other:
+
+- Homebrew's public repositories on GitHub
+- Homebrew's group communications between more than two maintainers on private channels (e.g. GitHub/Slack/Discourse)
+- Homebrew's direct 1:1 messages between two maintainers on private channels (e.g. iMessage/Slack/Discourse/IRC/carrier pigeon)
+
+All communication should ideally occur in public on GitHub. Where this is not possible or appropriate (e.g. a security disclosure, interpersonal issue between two maintainers, urgent breakage that needs to be resolved) this can move to maintainers' private group communication and, if necessary, 1:1 communication. Technical decisions should not happen in 1:1 communications but if they do (or did in the past) they must end up back as something linkable on GitHub. For example, if a technical decision was made a year ago on Slack and another maintainer/contributor/user asks about it on GitHub, that's a good chance to explain it to them and have something that can be linked to in the future.
+
+This makes it easier for other maintainers, contributors and users to follow along with what we're doing (and, more importantly, why we're doing it) and means that decisions have a linkable URL.
diff --git a/docs/Manpage.md b/docs/Manpage.md
index 3479ec771d..86baa20206 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -340,6 +340,8 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     If `--hide=``hidden` is passed, act as if none of `hidden` are installed.
     `hidden` should be a comma-separated list of formulae.
 
+    `missing` exits with a non-zero status if any formulae are missing dependencies.
+
   * `options` [`--compact`] (`--all`|`--installed`|`formulae`):
     Display install options specific to `formulae`.
 
@@ -378,9 +380,7 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
 
   * `prune` [`--dry-run`]:
     Remove dead symlinks from the Homebrew prefix. This is generally not
-    needed, but can be useful when doing DIY installations. Also remove broken
-    app symlinks from `/Applications` and `~/Applications` that were previously
-    created by `brew linkapps`.
+    needed, but can be useful when doing DIY installations.
 
     If `--dry-run` or `-n` is passed, show what would be removed, but do not
     actually remove anything.
@@ -444,13 +444,13 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
 
     Exits with a non-zero status if any style violations are found.
 
-  * `switch` `name` `version`:
-    Symlink all of the specific `version` of `name`'s install to Homebrew prefix.
+  * `switch` `formula` `version`:
+    Symlink all of the specific `version` of `formula`'s install to Homebrew prefix.
 
   * `tap`:
     List all installed taps.
 
-  * `tap` [`--full`] `user``/``repo` [`URL`]:
+  * `tap` [`--full`] [`--force-auto-update`] `user``/``repo` [`URL`]:
     Tap a formula repository.
 
     With `URL` unspecified, taps a formula repository from GitHub using HTTPS.
@@ -467,6 +467,10 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     if `--full` is passed, a full clone will be used. To convert a shallow copy
     to a full copy, you can retap passing `--full` without first untapping.
 
+    By default, only taps hosted on GitHub are auto-updated (for performance
+    reasons). If `--force-auto-update` is passed, this tap will be auto-updated
+    even if it is not hosted on GitHub.
+
     `tap` is re-runnable and exits successfully if there's nothing to do.
     However, retapping with a different `URL` will cause an exception, so first
     `untap` if you need to modify the `URL`.
@@ -474,9 +478,6 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
   * `tap` `--repair`:
     Migrate tapped formulae from symlink-based to directory-based structure.
 
-  * `tap` `--list-official`:
-    List all official taps.
-
   * `tap` `--list-pinned`:
     List all pinned taps.
 
@@ -669,7 +670,7 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     `audit` exits with a non-zero status if any errors are found. This is useful,
     for instance, for implementing pre-commit hooks.
 
-  * `bottle` [`--verbose`] [`--no-rebuild`|`--keep-old`] [`--skip-relocation`] [`--root-url=``URL`] [`--force-core-tap`] `formulae`:
+  * `bottle` [`--verbose`] [`--no-rebuild`|`--keep-old`] [`--skip-relocation`] [`--or-later`] [`--root-url=``URL`] [`--force-core-tap`] `formulae`:
     Generate a bottle (binary package) from a formula installed with
     `--build-bottle`.
 
@@ -686,6 +687,8 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
     If `--root-url` is passed, use the specified `URL` as the root of the
     bottle's URL instead of Homebrew's default.
 
+    If `--or-later` is passed, append _or_later to the bottle tag.
+
     If `--force-core-tap` is passed, build a bottle even if `formula` is not
     in homebrew/core or any installed taps.
 
@@ -853,7 +856,7 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
 
   * `release-notes` [`--markdown`] [`previous_tag`] [`end_ref`]:
     Output the merged pull requests on Homebrew/brew between two Git refs.
-    If no `previous_tag` is provided it defaults to the newest tag.
+    If no `previous_tag` is provided it defaults to the latest tag.
     If no `end_ref` is provided it defaults to `origin/master`.
 
     If `--markdown` is passed, output as a Markdown list.
@@ -1079,6 +1082,8 @@ can take several different forms:
     The formula file will be cached for later use.
 
 ## ENVIRONMENT
+Note that environment variables must have a value set to be detected. For example, `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just `export HOMEBREW_NO_INSECURE_REDIRECT`.
+
   * `HOMEBREW_ARTIFACT_DOMAIN`:
     If set, instructs Homebrew to use the given URL as a download mirror for bottles and binaries.
 
@@ -1113,6 +1118,10 @@ can take several different forms:
 
     *Default:* `~/Library/Caches/Homebrew`.
 
+  * `HOMEBREW_CURLRC`:
+    If set, Homebrew will not pass `-q` when invoking `curl`(1) (which disables
+    the use of `curlrc`).
+
   * `HOMEBREW_CURL_VERBOSE`:
     If set, Homebrew will pass `--verbose` when invoking `curl`(1).
 
diff --git a/docs/New-Maintainer-Checklist.md b/docs/New-Maintainer-Checklist.md
index cb4919d697..628437e2ea 100644
--- a/docs/New-Maintainer-Checklist.md
+++ b/docs/New-Maintainer-Checklist.md
@@ -55,7 +55,7 @@ If they accept, follow a few steps to get them set up:
 - Add them to the [Jenkins' GitHub Authorization Settings admin user names](https://jenkins.brew.sh/configureSecurity/) so they can adjust settings and restart jobs
 - Add them to the [Jenkins' GitHub Pull Request Builder admin list](https://jenkins.brew.sh/configure) to enable `@BrewTestBot test this please` for them
 - Invite them to the [`homebrew-maintainers` private maintainers mailing list](https://lists.sfconservancy.org/mailman/admin/homebrew-maintainers/members/add)
-- Invite them to the [`machomebrew` private maintainers Slack](https://machomebrew.slack.com/admin/invites)
+- Invite them to the [`machomebrew` private maintainers Slack](https://machomebrew.slack.com/admin/invites) (and ensure they've read the [communication guidelines](Maintainer-Guidelines.md#communication))
 - Invite them to the [`homebrew` private maintainers 1Password](https://homebrew.1password.com/signin)
 - Invite them to [Google Analytics](https://analytics.google.com/analytics/web/?authuser=1#management/Settings/a76679469w115400090p120682403/%3Fm.page%3DAccountUsers/)
 
diff --git a/docs/Troubleshooting.md b/docs/Troubleshooting.md
index 8b1bd73127..9ef0843a1c 100644
--- a/docs/Troubleshooting.md
+++ b/docs/Troubleshooting.md
@@ -17,7 +17,7 @@ Follow these steps to fix common problems:
 ## Check to see if the issue has been reported
 
 * Search the [issue tracker](https://github.com/Homebrew/homebrew-core/issues) to see if someone else has already reported the same issue.
-* Make sure you search issues on the correct repository. If a formula that has failed to build is part of a tap like [homebrew/php](https://github.com/Homebrew/homebrew-php/issues) or a cask is part of [caskroom/cask](https://github.com/caskroom/homebrew-cask/issues) check those issue trackers instead.
+* Make sure you search issues on the correct repository. If a formula that has failed to build is part of a non-homebrew-core tap or a cask is part of [caskroom/cask](https://github.com/caskroom/homebrew-cask/issues) check those issue trackers instead.
 
 ## Create an issue
 
diff --git a/manpages/brew-cask.1 b/manpages/brew-cask.1
index 6b32a90518..346c45d6a8 100644
--- a/manpages/brew-cask.1
+++ b/manpages/brew-cask.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW\-CASK" "1" "March 2018" "Homebrew" "brew-cask"
+.TH "BREW\-CASK" "1" "April 2018" "Homebrew" "brew-cask"
 .
 .SH "NAME"
 \fBbrew\-cask\fR \- a friendly binary installer for macOS
diff --git a/manpages/brew.1 b/manpages/brew.1
index ca8c6f5f14..9d2811a6a3 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW" "1" "March 2018" "Homebrew" "brew"
+.TH "BREW" "1" "April 2018" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for macOS
@@ -346,6 +346,9 @@ Check the given \fIformulae\fR for missing dependencies\. If no \fIformulae\fR a
 .IP
 If \fB\-\-hide=\fR\fIhidden\fR is passed, act as if none of \fIhidden\fR are installed\. \fIhidden\fR should be a comma\-separated list of formulae\.
 .
+.IP
+\fBmissing\fR exits with a non\-zero status if any formulae are missing dependencies\.
+.
 .TP
 \fBoptions\fR [\fB\-\-compact\fR] (\fB\-\-all\fR|\fB\-\-installed\fR|\fIformulae\fR)
 Display install options specific to \fIformulae\fR\.
@@ -388,7 +391,7 @@ Rerun the post\-install steps for \fIformula\fR\.
 .
 .TP
 \fBprune\fR [\fB\-\-dry\-run\fR]
-Remove dead symlinks from the Homebrew prefix\. This is generally not needed, but can be useful when doing DIY installations\. Also remove broken app symlinks from \fB/Applications\fR and \fB~/Applications\fR that were previously created by \fBbrew linkapps\fR\.
+Remove dead symlinks from the Homebrew prefix\. This is generally not needed, but can be useful when doing DIY installations\.
 .
 .IP
 If \fB\-\-dry\-run\fR or \fB\-n\fR is passed, show what would be removed, but do not actually remove anything\.
@@ -455,15 +458,15 @@ Passing \fB\-\-only\-cops=\fR\fIcops\fR will check for violations of only the li
 Exits with a non\-zero status if any style violations are found\.
 .
 .TP
-\fBswitch\fR \fIname\fR \fIversion\fR
-Symlink all of the specific \fIversion\fR of \fIname\fR\'s install to Homebrew prefix\.
+\fBswitch\fR \fIformula\fR \fIversion\fR
+Symlink all of the specific \fIversion\fR of \fIformula\fR\'s install to Homebrew prefix\.
 .
 .TP
 \fBtap\fR
 List all installed taps\.
 .
 .TP
-\fBtap\fR [\fB\-\-full\fR] \fIuser\fR\fB/\fR\fIrepo\fR [\fIURL\fR]
+\fBtap\fR [\fB\-\-full\fR] [\fB\-\-force\-auto\-update\fR] \fIuser\fR\fB/\fR\fIrepo\fR [\fIURL\fR]
 Tap a formula repository\.
 .
 .IP
@@ -476,6 +479,9 @@ With \fIURL\fR specified, taps a formula repository from anywhere, using any tra
 By default, the repository is cloned as a shallow copy (\fB\-\-depth=1\fR), but if \fB\-\-full\fR is passed, a full clone will be used\. To convert a shallow copy to a full copy, you can retap passing \fB\-\-full\fR without first untapping\.
 .
 .IP
+By default, only taps hosted on GitHub are auto\-updated (for performance reasons)\. If \fB\-\-force\-auto\-update\fR is passed, this tap will be auto\-updated even if it is not hosted on GitHub\.
+.
+.IP
 \fBtap\fR is re\-runnable and exits successfully if there\'s nothing to do\. However, retapping with a different \fIURL\fR will cause an exception, so first \fBuntap\fR if you need to modify the \fIURL\fR\.
 .
 .TP
@@ -483,10 +489,6 @@ By default, the repository is cloned as a shallow copy (\fB\-\-depth=1\fR), but
 Migrate tapped formulae from symlink\-based to directory\-based structure\.
 .
 .TP
-\fBtap\fR \fB\-\-list\-official\fR
-List all official taps\.
-.
-.TP
 \fBtap\fR \fB\-\-list\-pinned\fR
 List all pinned taps\.
 .
@@ -686,7 +688,7 @@ Passing \fB\-\-only\-cops=\fR\fIcops\fR will check for violations of only the li
 \fBaudit\fR exits with a non\-zero status if any errors are found\. This is useful, for instance, for implementing pre\-commit hooks\.
 .
 .TP
-\fBbottle\fR [\fB\-\-verbose\fR] [\fB\-\-no\-rebuild\fR|\fB\-\-keep\-old\fR] [\fB\-\-skip\-relocation\fR] [\fB\-\-root\-url=\fR\fIURL\fR] [\fB\-\-force\-core\-tap\fR] \fIformulae\fR
+\fBbottle\fR [\fB\-\-verbose\fR] [\fB\-\-no\-rebuild\fR|\fB\-\-keep\-old\fR] [\fB\-\-skip\-relocation\fR] [\fB\-\-or\-later\fR] [\fB\-\-root\-url=\fR\fIURL\fR] [\fB\-\-force\-core\-tap\fR] \fIformulae\fR
 Generate a bottle (binary package) from a formula installed with \fB\-\-build\-bottle\fR\.
 .
 .IP
@@ -702,6 +704,9 @@ If \fB\-\-skip\-relocation\fR is passed, do not check if the bottle can be marke
 If \fB\-\-root\-url\fR is passed, use the specified \fIURL\fR as the root of the bottle\'s URL instead of Homebrew\'s default\.
 .
 .IP
+If \fB\-\-or\-later\fR is passed, append _or_later to the bottle tag\.
+.
+.IP
 If \fB\-\-force\-core\-tap\fR is passed, build a bottle even if \fIformula\fR is not in homebrew/core or any installed taps\.
 .
 .TP
@@ -869,7 +874,7 @@ If \fB\-\-test\-bot\-user=\fR\fItest\-bot\-user\fR is passed, pull the bottle bl
 .
 .TP
 \fBrelease\-notes\fR [\fB\-\-markdown\fR] [\fIprevious_tag\fR] [\fIend_ref\fR]
-Output the merged pull requests on Homebrew/brew between two Git refs\. If no \fIprevious_tag\fR is provided it defaults to the newest tag\. If no \fIend_ref\fR is provided it defaults to \fBorigin/master\fR\.
+Output the merged pull requests on Homebrew/brew between two Git refs\. If no \fIprevious_tag\fR is provided it defaults to the latest tag\. If no \fIend_ref\fR is provided it defaults to \fBorigin/master\fR\.
 .
 .IP
 If \fB\-\-markdown\fR is passed, output as a Markdown list\.
@@ -1096,6 +1101,7 @@ An arbitrary URL
 Homebrew can install formulae via URL, e\.g\. \fBhttps://raw\.github\.com/Homebrew/homebrew\-core/master/Formula/git\.rb\fR\. The formula file will be cached for later use\.
 .
 .SH "ENVIRONMENT"
+Note that environment variables must have a value set to be detected\. For example, \fBexport HOMEBREW_NO_INSECURE_REDIRECT=1\fR rather than just \fBexport HOMEBREW_NO_INSECURE_REDIRECT\fR\.
 .
 .TP
 \fBHOMEBREW_ARTIFACT_DOMAIN\fR
@@ -1132,6 +1138,10 @@ If set, instructs Homebrew to use the given directory as the download cache\.
 \fIDefault:\fR \fB~/Library/Caches/Homebrew\fR\.
 .
 .TP
+\fBHOMEBREW_CURLRC\fR
+If set, Homebrew will not pass \fB\-q\fR when invoking \fBcurl\fR(1) (which disables the use of \fBcurlrc\fR)\.
+.
+.TP
 \fBHOMEBREW_CURL_VERBOSE\fR
 If set, Homebrew will pass \fB\-\-verbose\fR when invoking \fBcurl\fR(1)\.
 .