Merge branch 'master' into audit_line_rubocop_part_4_rebase_attempt_1

Library/.rubocop.yml

@@ -29,7 +29,7 @@ Layout/IndentArray:
   EnforcedStyle: special_inside_parentheses
 
 Layout/IndentHeredoc:
-  EnforcedStyle: unindent
+  EnforcedStyle: squiggly
 
 # conflicts with DSL-style path concatenation with `/`
 Layout/SpaceAroundOperators:
@@ -73,6 +73,8 @@ Metrics/CyclomaticComplexity:
 
 Metrics/LineLength:
   Max: 324
+  # ignore manpage comments
+  IgnoredPatterns: ['#: ']
 
 Metrics/MethodLength:
   Max: 222

Library/Homebrew/cask/lib/hbc/artifact/abstract_uninstall.rb

@@ -253,7 +253,7 @@ module Hbc
       end
 
       def trash_paths(*paths, command: nil, **_)
-        result = command.run!("/usr/bin/osascript", args: ["-e", <<-'EOS'.undent, *paths])
+        result = command.run!("/usr/bin/osascript", args: ["-e", <<~'EOS', *paths])
           on run argv
             repeat with i from 1 to (count argv)
               set item i of argv to (item i of argv as POSIX file)

Library/Homebrew/cask/lib/hbc/artifact/installer.rb

@@ -10,7 +10,7 @@ module Hbc
 
       module ManualInstaller
         def install_phase(**)
-          puts <<-EOS.undent
+          puts <<~EOS
             To complete the installation of Cask #{cask}, you must also
             run the installer at
 

Library/Homebrew/cask/lib/hbc/audit.rb

@@ -174,7 +174,7 @@ module Hbc
         add_warning "error retrieving appcast: #{result[:command_result].stderr}"
       else
         expected = cask.appcast.checkpoint
-        add_warning <<-EOS.undent unless expected == actual_checkpoint
+        add_warning <<~EOS unless expected == actual_checkpoint
           appcast checkpoint mismatch
           Expected: #{expected}
           Actual: #{actual_checkpoint}

Library/Homebrew/cask/lib/hbc/cask_loader.rb

@@ -190,7 +190,7 @@ module Hbc
       when 2..Float::INFINITY
         loaders = possible_tap_casks.map(&FromTapPathLoader.method(:new))
 
-        raise CaskError, <<-EOS.undent
+        raise CaskError, <<~EOS
           Cask #{ref} exists in multiple taps:
           #{loaders.map { |loader| "  #{loader.tap}/#{loader.token}" }.join("\n")}
         EOS

Library/Homebrew/cask/lib/hbc/cli.rb

@@ -235,7 +235,7 @@ module Hbc
       end
 
       def purpose
-        puts <<-EOS.undent
+        puts <<~EOS
           brew-cask provides a friendly homebrew-style CLI workflow for the
           administration of macOS applications distributed as binaries.
 

Library/Homebrew/cask/lib/hbc/cli/create.rb

@@ -21,7 +21,7 @@ module Hbc
       end
 
       def self.template(cask_token)
-        <<-EOS.undent
+        <<~EOS
           cask '#{cask_token}' do
             version ''
             sha256 ''

Library/Homebrew/cask/lib/hbc/cli/internal_audit_modified_casks.rb

@@ -16,7 +16,7 @@ module Hbc
         super
 
         if args.count != 1
-          raise ArgumentError, <<-EOS.undent
+          raise ArgumentError, <<~EOS
             This command requires exactly one argument.
 
             #{self.class.usage}
@@ -31,7 +31,7 @@ module Hbc
       end
 
       def self.usage
-        <<-EOS.undent
+        <<~EOS
           Usage: brew cask _audit_modified_casks [options...] <commit range>
 
           Given a range of Git commits, find any Casks that were modified and run `brew

Library/Homebrew/cask/lib/hbc/cli/uninstall.rb

@@ -25,7 +25,7 @@ module Hbc
 
           single = versions.count == 1
 
-          puts <<-EOS.undent
+          puts <<~EOS
             #{cask} #{versions.join(", ")} #{single ? "is" : "are"} still installed.
             Remove #{single ? "it" : "them all"} with `brew cask uninstall --force #{cask}`.
           EOS

Library/Homebrew/cask/lib/hbc/container/air.rb

@@ -13,7 +13,7 @@ module Hbc
 
       def self.installer_cmd
         return @installer_cmd ||= INSTALLER_PATHNAME if installer_exist?
-        raise CaskError, <<-EOS.undent
+        raise CaskError, <<~EOS
           Adobe AIR runtime not present, try installing it via
 
               brew cask install adobe-air

Library/Homebrew/cask/lib/hbc/dsl/caveats.rb

@@ -9,22 +9,22 @@ module Hbc
   class DSL
     class Caveats < Base
       def path_environment_variable(path)
-        puts <<-EOS.undent
+        puts <<~EOS
-        To use #{@cask}, you may need to add the #{path} directory
+          To use #{@cask}, you may need to add the #{path} directory
-        to your PATH environment variable, eg (for bash shell):
+          to your PATH environment variable, eg (for bash shell):
 
-          export PATH=#{path}:"$PATH"
+            export PATH=#{path}:"$PATH"
 
         EOS
       end
 
       def zsh_path_helper(path)
-        puts <<-EOS.undent
+        puts <<~EOS
-        To use #{@cask}, zsh users may need to add the following line to their
+          To use #{@cask}, zsh users may need to add the following line to their
-        ~/.zprofile.  (Among other effects, #{path} will be added to the
+          ~/.zprofile.  (Among other effects, #{path} will be added to the
-        PATH environment variable):
+          PATH environment variable):
 
-          eval `/usr/libexec/path_helper -s`
+            eval `/usr/libexec/path_helper -s`
 
         EOS
       end
@@ -32,7 +32,7 @@ module Hbc
       def files_in_usr_local
         localpath = "/usr/local"
         return unless HOMEBREW_PREFIX.to_s.downcase.start_with?(localpath)
-        puts <<-EOS.undent
+        puts <<~EOS
           Cask #{@cask} installs files under "#{localpath}". The presence of such
           files can cause warnings when running "brew doctor", which is considered
           to be a bug in Homebrew-Cask.
@@ -42,72 +42,72 @@ module Hbc
 
       def depends_on_java(java_version = "any")
         if java_version == "any"
-          puts <<-EOS.undent
+          puts <<~EOS
-          #{@cask} requires Java. You can install the latest version with
+            #{@cask} requires Java. You can install the latest version with
 
-            brew cask install java
+              brew cask install java
 
           EOS
         elsif java_version.include?("9") || java_version.include?("+")
-          puts <<-EOS.undent
+          puts <<~EOS
-          #{@cask} requires Java #{java_version}. You can install the latest version with
+            #{@cask} requires Java #{java_version}. You can install the latest version with
 
-            brew cask install java
+              brew cask install java
 
           EOS
         else
-          puts <<-EOS.undent
+          puts <<~EOS
-          #{@cask} requires Java #{java_version}. You can install it with
+            #{@cask} requires Java #{java_version}. You can install it with
 
-            brew cask install caskroom/versions/java#{java_version}
+              brew cask install caskroom/versions/java#{java_version}
 
           EOS
         end
       end
 
       def logout
-        puts <<-EOS.undent
+        puts <<~EOS
-        You must log out and log back in for the installation of #{@cask}
+          You must log out and log back in for the installation of #{@cask}
-        to take effect.
+          to take effect.
 
         EOS
       end
 
       def reboot
-        puts <<-EOS.undent
+        puts <<~EOS
-        You must reboot for the installation of #{@cask} to take effect.
+          You must reboot for the installation of #{@cask} to take effect.
 
         EOS
       end
 
       def discontinued
-        puts <<-EOS.undent
+        puts <<~EOS
-        #{@cask} has been officially discontinued upstream.
+          #{@cask} has been officially discontinued upstream.
-        It may stop working correctly (or at all) in recent versions of macOS.
+          It may stop working correctly (or at all) in recent versions of macOS.
 
         EOS
       end
 
       def free_license(web_page)
-        puts <<-EOS.undent
+        puts <<~EOS
-        The vendor offers a free license for #{@cask} at
+          The vendor offers a free license for #{@cask} at
-          #{web_page}
+            #{web_page}
 
         EOS
       end
 
       def malware(radar_number)
-        puts <<-EOS.undent
+        puts <<~EOS
-        #{@cask} has been reported to bundle malware. Like with any app, use at your own risk.
+          #{@cask} has been reported to bundle malware. Like with any app, use at your own risk.
 
-        A report has been made to Apple about this app. Their certificate will hopefully be revoked.
+          A report has been made to Apple about this app. Their certificate will hopefully be revoked.
-        See the public report at
+          See the public report at
-          #{Formatter.url("https://openradar.appspot.com/#{radar_number}")}
+            #{Formatter.url("https://openradar.appspot.com/#{radar_number}")}
 
-        If this report is accurate, please duplicate it at
+          If this report is accurate, please duplicate it at
-          #{Formatter.url("https://bugreport.apple.com/")}
+            #{Formatter.url("https://bugreport.apple.com/")}
-        If this report is a mistake, please let us know by opening an issue at
+          If this report is a mistake, please let us know by opening an issue at
-          #{Formatter.url("https://github.com/caskroom/homebrew-cask/issues/new")}
+            #{Formatter.url("https://github.com/caskroom/homebrew-cask/issues/new")}
 
         EOS
       end

Library/Homebrew/cask/lib/hbc/exceptions.rb

@@ -44,7 +44,7 @@ module Hbc
 
   class CaskAlreadyInstalledError < AbstractCaskErrorWithToken
     def to_s
-      <<-EOS.undent
+      <<~EOS
         Cask '#{token}' is already installed.
 
         To re-install #{token}, run:
@@ -80,7 +80,7 @@ module Hbc
 
   class CaskX11DependencyError < AbstractCaskErrorWithToken
     def to_s
-      <<-EOS.undent
+      <<~EOS
         Cask '#{token}' requires XQuartz/X11, which can be installed using Homebrew-Cask by running
           #{Formatter.identifier("brew cask install xquartz")}
 
@@ -132,7 +132,7 @@ module Hbc
 
   class CaskSha256MissingError < CaskSha256Error
     def to_s
-      <<-EOS.undent
+      <<~EOS
         Cask '#{token}' requires a checksum:
           #{Formatter.identifier("sha256 '#{actual}'")}
       EOS
@@ -148,7 +148,7 @@ module Hbc
     end
 
     def to_s
-      <<-EOS.undent
+      <<~EOS
         Checksum for Cask '#{token}' does not match.
 
         Expected: #{Formatter.success(expected.to_s)}
@@ -162,7 +162,7 @@ module Hbc
 
   class CaskNoShasumError < CaskSha256Error
     def to_s
-      <<-EOS.undent
+      <<~EOS
         Cask '#{token}' does not have a sha256 checksum defined and was not installed.
         This means you have the #{Formatter.identifier("--require-sha")} option set, perhaps in your HOMEBREW_CASK_OPTS.
       EOS

Library/Homebrew/cask/lib/hbc/installer.rb

@@ -326,7 +326,7 @@ module Hbc
                       ],
                       sudo: true)
       else
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Accessibility access cannot be enabled automatically on this version of macOS.
           See System Preferences to enable it manually.
         EOS
@@ -347,7 +347,7 @@ module Hbc
                       ],
                       sudo: true)
       else
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Accessibility access cannot be disabled automatically on this version of macOS.
           See System Preferences to disable it manually.
         EOS

Library/Homebrew/cask/lib/hbc/system_command.rb

@@ -166,12 +166,12 @@ module Hbc
         _warn_plist_garbage(command, Regexp.last_match[2])
         xml = Plist.parse_xml(output)
         unless xml.respond_to?(:keys) && !xml.keys.empty?
-          raise CaskError, <<-EOS
+          raise CaskError, <<~EOS
-    Empty result parsing plist output from command.
+            Empty result parsing plist output from command.
-      command was:
+              command was:
-      #{command}
+              #{command}
-      output we attempted to parse:
+              output we attempted to parse:
-      #{output}
+              #{output}
           EOS
         end
         xml

Library/Homebrew/cask/lib/hbc/utils.rb

@@ -90,7 +90,7 @@ module Hbc
     end
 
     def self.error_message_with_suggestions
-      <<-EOS.undent
+      <<~EOS
         Follow the instructions here:
           #{Formatter.url(BUG_REPORTS_URL)}
       EOS

Library/Homebrew/cask/lib/hbc/version.rb

@@ -1,7 +1,7 @@
 module Hbc
   def self.full_version
     @full_version ||= begin
-      <<-EOS.undent
+      <<~EOS
         Homebrew-Cask #{HOMEBREW_VERSION}
         caskroom/homebrew-cask #{Hbc.default_tap.version_string}
       EOS

Library/Homebrew/caveats.rb

@@ -44,7 +44,7 @@ class Caveats
   def keg_only_text
     return unless f.keg_only?
 
-    s = <<-EOS.undent
+    s = <<~EOS
       This formula is keg-only, which means it was not symlinked into #{HOMEBREW_PREFIX},
       because #{f.keg_only_reason.to_s.chomp}.
     EOS
@@ -86,12 +86,12 @@ class Caveats
 
     case shell
     when :bash
-      <<-EOS.undent
+      <<~EOS
         Bash completion has been installed to:
           #{HOMEBREW_PREFIX}/etc/bash_completion.d
       EOS
     when :zsh
-      <<-EOS.undent
+      <<~EOS
         zsh #{installed.join(" and ")} have been installed to:
           #{HOMEBREW_PREFIX}/share/zsh/site-functions
       EOS
@@ -111,7 +111,7 @@ class Caveats
     homebrew_site_packages = Language::Python.homebrew_site_packages
     user_site_packages = Language::Python.user_site_packages "python"
     pth_file = user_site_packages/"homebrew.pth"
-    instructions = <<-EOS.undent.gsub(/^/, "  ")
+    instructions = <<~EOS.gsub(/^/, "  ")
       mkdir -p #{user_site_packages}
       echo 'import site; site.addsitedir("#{homebrew_site_packages}")' >> #{pth_file}
     EOS
@@ -119,7 +119,7 @@ class Caveats
     if f.keg_only?
       keg_site_packages = f.opt_prefix/"lib/python2.7/site-packages"
       unless Language::Python.in_sys_path?("python", keg_site_packages)
-        s = <<-EOS.undent
+        s = <<~EOS
           If you need Python to find bindings for this keg-only formula, run:
             echo #{keg_site_packages} >> #{homebrew_site_packages/f.name}.pth
         EOS
@@ -131,7 +131,7 @@ class Caveats
     return if Language::Python.reads_brewed_pth_files?("python")
 
     if !Language::Python.in_sys_path?("python", homebrew_site_packages)
-      s = <<-EOS.undent
+      s = <<~EOS
         Python modules have been installed and Homebrew's site-packages is not
         in your Python sys.path, so you will not be able to import the modules
         this formula installed. If you plan to develop with these modules,
@@ -139,7 +139,7 @@ class Caveats
       EOS
       s += instructions
     elsif keg.python_pth_files_installed?
-      s = <<-EOS.undent
+      s = <<~EOS
         This formula installed .pth files to Homebrew's site-packages and your
         Python isn't configured to process them, so you will not be able to
         import the modules this formula installed. If you plan to develop
@@ -155,55 +155,13 @@ class Caveats
     return unless keg
     return unless keg.elisp_installed?
 
-    <<-EOS.undent
+    <<~EOS
       Emacs Lisp files have been installed to:
         #{HOMEBREW_PREFIX}/share/emacs/site-lisp/#{f.name}
     EOS
   end
 
-  def plist_caveats
+  def plist_caveats; end
-    s = []
-    if f.plist || (keg&.plist_installed?)
-      plist_domain = f.plist_path.basename(".plist")
-
-      # we readlink because this path probably doesn't exist since caveats
-      # occurs before the link step of installation
-      # Yosemite security measures mildly tighter rules:
-      # https://github.com/Homebrew/legacy-homebrew/issues/33815
-      if !plist_path.file? || !plist_path.symlink?
-        if f.plist_startup
-          s << "To have launchd start #{f.full_name} now and restart at startup:"
-          s << "  sudo brew services start #{f.full_name}"
-        else
-          s << "To have launchd start #{f.full_name} now and restart at login:"
-          s << "  brew services start #{f.full_name}"
-        end
-      # For startup plists, we cannot tell whether it's running on launchd,
-      # as it requires for `sudo launchctl list` to get real result.
-      elsif f.plist_startup
-        s << "To restart #{f.full_name} after an upgrade:"
-        s << "  sudo brew services restart #{f.full_name}"
-      elsif Kernel.system "/bin/launchctl list #{plist_domain} &>/dev/null"
-        s << "To restart #{f.full_name} after an upgrade:"
-        s << "  brew services restart #{f.full_name}"
-      else
-        s << "To start #{f.full_name}:"
-        s << "  brew services start #{f.full_name}"
-      end
-
-      if f.plist_manual
-        s << "Or, if you don't want/need a background service you can just run:"
-        s << "  #{f.plist_manual}"
-      end
-
-      # pbpaste is the system clipboard tool on macOS and fails with `tmux` by default
-      # check if this is being run under `tmux` to avoid failing
-      if ENV["TMUX"] && !quiet_system("/usr/bin/pbpaste")
-        s << "" << "WARNING: brew services will fail when run under tmux."
-      end
-    end
-    s.join("\n") + "\n" unless s.empty?
-  end
 
   def plist_path
     destination = if f.plist_startup
@@ -222,3 +180,5 @@ class Caveats
     destination_path/plist_filename
   end
 end
+
+require "extend/os/caveats"

Library/Homebrew/cmd/cleanup.rb

@@ -38,7 +38,7 @@ module Homebrew
   end
 
   def report_unremovable_kegs
-    ofail <<-EOS.undent
+    ofail <<~EOS
       Could not cleanup old kegs! Fix your permissions on:
         #{Cleanup.unremovable_kegs.join "\n  "}
     EOS

Library/Homebrew/cmd/commands.rb

@@ -16,12 +16,12 @@ module Homebrew
     else
       # Find commands in Homebrew/cmd
       puts "Built-in commands"
-      puts Formatter.columns(internal_commands)
+      puts Formatter.columns(internal_commands.sort)
 
       # Find commands in Homebrew/dev-cmd
       puts
       puts "Built-in developer commands"
-      puts Formatter.columns(internal_developer_commands)
+      puts Formatter.columns(internal_developer_commands.sort)
 
       # Find commands in the path
       unless (exts = external_commands).empty?
@@ -51,8 +51,8 @@ module Homebrew
   end
 
   def find_internal_commands(directory)
-    directory.children.each_with_object([]) do |f, cmds|
+    Pathname.glob(directory/"*")
-      cmds << f.basename.to_s.sub(/\.(?:rb|sh)$/, "") if f.file?
+            .select(&:file?)
-    end
+            .map { |f| f.basename.to_s.sub(/\.(?:rb|sh)$/, "") }
   end
 end

Library/Homebrew/cmd/deps.rb

@@ -68,16 +68,16 @@ module Homebrew
 
     if mode.tree?
       if mode.installed?
-        puts_deps_tree Formula.installed, !ARGV.one?
+        puts_deps_tree Formula.installed.sort, !ARGV.one?
       else
         raise FormulaUnspecifiedError if ARGV.named.empty?
         puts_deps_tree ARGV.formulae, !ARGV.one?
       end
     elsif mode.all?
-      puts_deps Formula
+      puts_deps Formula.sort
     elsif ARGV.named.empty?
       raise FormulaUnspecifiedError unless mode.installed?
-      puts_deps Formula.installed
+      puts_deps Formula.installed.sort
     elsif mode.for_each?
       puts_deps ARGV.formulae
     else

Library/Homebrew/cmd/diy.rb

@@ -43,7 +43,7 @@ module Homebrew
     detected_name = basename[/(.*?)-?#{Regexp.escape(version)}/, 1] || basename
     canonical_name = Formulary.canonical_name(detected_name)
 
-    odie <<-EOS.undent if detected_name != canonical_name
+    odie <<~EOS if detected_name != canonical_name
       The detected name #{detected_name.inspect} exists in Homebrew as an alias
       of #{canonical_name.inspect}. Consider using the canonical name instead:
         brew diy --name=#{canonical_name}

Library/Homebrew/cmd/doctor.rb

@@ -43,7 +43,7 @@ module Homebrew
       out = checks.send(method)
       next if out.nil? || out.empty?
       if first_warning
-        $stderr.puts <<-EOS.undent
+        $stderr.puts <<~EOS
           #{Tty.bold}Please note that these warnings are just used to help the Homebrew maintainers
           with debugging if you file an issue. If everything you use Homebrew for is
           working fine: please don't worry and just ignore them. Thanks!#{Tty.reset}

Library/Homebrew/cmd/gist-logs.rb

@@ -29,7 +29,7 @@ module Homebrew
     files["00.config.out"] = { content: s.string }
     files["00.doctor.out"] = { content: `brew doctor 2>&1` }
     unless f.core_formula?
-      tap = <<-EOS.undent
+      tap = <<~EOS
         Formula: #{f.name}
         Tap: #{f.tap}
         Path: #{f.path}
@@ -47,7 +47,7 @@ module Homebrew
 
     if ARGV.include?("--new-issue") || ARGV.switch?("n")
       if GitHub.api_credentials_type == :none
-        puts <<-EOS.undent
+        puts <<~EOS
           You can create a new personal access token:
            #{GitHub::ALL_SCOPES_URL}
           and then set the new HOMEBREW_GITHUB_API_TOKEN as the authentication method.
@@ -64,7 +64,7 @@ module Homebrew
 
   def brief_build_info(f)
     build_time_str = f.logs.ctime.strftime("%Y-%m-%d %H:%M:%S")
-    s = <<-EOS.undent
+    s = <<~EOS
       Homebrew build logs for #{f.full_name} on #{OS_VERSION}
     EOS
     if ARGV.include?("--with-hostname")

Library/Homebrew/cmd/help.rb

@@ -1,4 +1,4 @@
-HOMEBREW_HELP = <<-EOS.unindent.freeze
+HOMEBREW_HELP = <<~EOS.freeze
   Example usage:
     brew search [TEXT|/REGEX/]
     brew (info|home|options) [FORMULA...]

Library/Homebrew/cmd/info.rb

@@ -67,9 +67,9 @@ module Homebrew
 
   def print_json
     ff = if ARGV.include? "--all"
-      Formula
+      Formula.sort
     elsif ARGV.include? "--installed"
-      Formula.installed
+      Formula.installed.sort
     else
       ARGV.formulae
     end
@@ -128,7 +128,7 @@ module Homebrew
       "#{c.name}#{reason}"
     end.sort!
     unless conflicts.empty?
-      puts <<-EOS.undent
+      puts <<~EOS
         Conflicts with:
           #{conflicts.join("\n  ")}
       EOS

Library/Homebrew/cmd/install.rb

@@ -110,17 +110,17 @@ module Homebrew
       ARGV.formulae.each do |f|
         # head-only without --HEAD is an error
         if !ARGV.build_head? && f.stable.nil? && f.devel.nil?
-          raise <<-EOS.undent
+          raise <<~EOS
-          #{f.full_name} is a head-only formula
+            #{f.full_name} is a head-only formula
-          Install with `brew install --HEAD #{f.full_name}`
+            Install with `brew install --HEAD #{f.full_name}`
           EOS
         end
 
         # devel-only without --devel is an error
         if !ARGV.build_devel? && f.stable.nil? && f.head.nil?
-          raise <<-EOS.undent
+          raise <<~EOS
-          #{f.full_name} is a devel-only formula
+            #{f.full_name} is a devel-only formula
-          Install with `brew install --devel #{f.full_name}`
+            Install with `brew install --devel #{f.full_name}`
           EOS
         end
 
@@ -150,12 +150,12 @@ module Homebrew
           # sure --force flag is passed.
           if f.outdated?
             optlinked_version = Keg.for(f.opt_prefix).version
-            onoe <<-EOS.undent
+            onoe <<~EOS
               #{f.full_name} #{optlinked_version} is already installed
               To upgrade to #{f.version}, run `brew upgrade #{f.name}`
             EOS
           else
-            opoo <<-EOS.undent
+            opoo <<~EOS
               #{f.full_name} #{f.pkg_version} is already installed
             EOS
           end
@@ -173,13 +173,13 @@ module Homebrew
           msg = "#{f.full_name} #{installed_version} is already installed"
           linked_not_equals_installed = f.linked_version != installed_version
           if f.linked? && linked_not_equals_installed
-            msg = <<-EOS.undent
+            msg = <<~EOS
               #{msg}
               The currently linked version is #{f.linked_version}
               You can use `brew switch #{f} #{installed_version}` to link this version.
             EOS
           elsif !f.linked? || f.keg_only?
-            msg = <<-EOS.undent
+            msg = <<~EOS
               #{msg}, it's just not linked.
               You can use `brew link #{f}` to link this version.
             EOS
@@ -188,7 +188,7 @@ module Homebrew
         elsif !f.any_version_installed? && old_formula = f.old_installed_formulae.first
           msg = "#{old_formula.full_name} #{old_formula.installed_version} already installed"
           if !old_formula.linked? && !old_formula.keg_only?
-            msg = <<-EOS.undent
+            msg = <<~EOS
               #{msg}, it's just not linked.
               You can use `brew link #{old_formula.full_name}` to link this version.
             EOS
@@ -197,7 +197,7 @@ module Homebrew
         elsif f.migration_needed? && !ARGV.force?
           # Check if the formula we try to install is the same as installed
           # but not migrated one. If --force passed then install anyway.
-          opoo <<-EOS.undent
+          opoo <<~EOS
             #{f.oldname} already installed, it's just not migrated
             You can migrate formula with `brew migrate #{f}`
             Or you can force install it with `brew install #{f} --force`
@@ -283,7 +283,7 @@ module Homebrew
   def check_ppc
     case Hardware::CPU.type
     when :ppc
-      abort <<-EOS.undent
+      abort <<~EOS
         Sorry, Homebrew does not support your computer's CPU architecture.
         For PPC support, see: https://github.com/mistydemeo/tigerbrew
       EOS
@@ -308,7 +308,7 @@ module Homebrew
   def check_cellar
     FileUtils.mkdir_p HOMEBREW_CELLAR unless File.exist? HOMEBREW_CELLAR
   rescue
-    raise <<-EOS.undent
+    raise <<~EOS
       Could not create #{HOMEBREW_CELLAR}
       Check you have permission to write to #{HOMEBREW_CELLAR.parent}
     EOS

Library/Homebrew/cmd/leaves.rb

@@ -9,7 +9,7 @@ module Homebrew
   module_function
 
   def leaves
-    installed = Formula.installed
+    installed = Formula.installed.sort
     deps_of_installed = Set.new
 
     installed.each do |f|

Library/Homebrew/cmd/link.rb

@@ -29,7 +29,7 @@ module Homebrew
       keg_only = keg_only?(keg.rack)
       if HOMEBREW_PREFIX.to_s == "/usr/local" && keg_only &&
          keg.name.start_with?("openssl", "libressl")
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Refusing to link: #{keg.name}
           Linking keg-only #{keg.name} means you may end up linking against the insecure,
           deprecated system OpenSSL while using the headers from Homebrew's #{keg.name}.

Library/Homebrew/cmd/linkapps.rb

@@ -19,7 +19,7 @@ module Homebrew
   module_function
 
   def linkapps
-    opoo <<-EOS.undent
+    opoo <<~EOS
       `brew linkapps` has been deprecated and will eventually be removed!
 
       Unfortunately `brew linkapps` cannot behave nicely with e.g. Spotlight using

Library/Homebrew/cmd/list.rb

@@ -39,7 +39,7 @@ module Homebrew
       filtered_list
     elsif ARGV.named.empty?
       if ARGV.include? "--full-name"
-        full_names = Formula.installed.map(&:full_name).sort &tap_and_name_comparison
+        full_names = Formula.installed.map(&:full_name).sort(&tap_and_name_comparison)
         return if full_names.empty?
         puts Formatter.columns(full_names)
       else
@@ -87,7 +87,7 @@ module Homebrew
     dirs.delete "etc"
     dirs.delete "var"
 
-    args = dirs + %w[-type f (]
+    args = dirs.sort + %w[-type f (]
     args.concat UNBREWED_EXCLUDE_FILES.flat_map { |f| %W[! -name #{f}] }
     args.concat UNBREWED_EXCLUDE_PATHS.flat_map { |d| %W[! -path #{d}] }
     args.concat %w[)]

Library/Homebrew/cmd/log.rb

@@ -31,7 +31,7 @@ module Homebrew
     end
 
     if File.exist? "#{repo}/.git/shallow"
-      opoo <<-EOS.undent
+      opoo <<~EOS
         #{name} is a shallow clone so only partial output will be shown.
         To get a full clone run:
           git -C "#{git_cd}" fetch --unshallow

Library/Homebrew/cmd/missing.rb

@@ -16,9 +16,9 @@ module Homebrew
     return unless HOMEBREW_CELLAR.exist?
 
     ff = if ARGV.named.empty?
-      Formula.installed
+      Formula.installed.sort
     else
-      ARGV.resolved_formulae
+      ARGV.resolved_formulae.sort
     end
 
     ff.each do |f|

Library/Homebrew/cmd/options.rb

@@ -16,9 +16,9 @@ module Homebrew
 
   def options
     if ARGV.include? "--all"
-      puts_options Formula.to_a
+      puts_options Formula.to_a.sort
     elsif ARGV.include? "--installed"
-      puts_options Formula.installed
+      puts_options Formula.installed.sort
     else
       raise FormulaUnspecifiedError if ARGV.named.empty?
       puts_options ARGV.formulae

Library/Homebrew/cmd/readall.rb

@@ -1,6 +1,7 @@
 #: @hide_from_man_page
 #:  * `readall` [tap]:
-#:    Import all formulae in a tap (defaults to core tap).
+#:    Import all formulae from specified taps (defaults to
+#:    all installed taps).
 #:
 #:    This can be useful for debugging issues across all formulae
 #:    when making significant changes to `formula.rb`,
@@ -13,16 +14,8 @@ module Homebrew
 
   def readall
     if ARGV.include?("--syntax")
-      ruby_files = []
+      scan_files = "#{HOMEBREW_LIBRARY_PATH}/**/*.rb"
-      scan_files = %W[
+      ruby_files = Dir.glob(scan_files).reject { |file| file =~ %r{/(vendor|cask)/} }
-        #{HOMEBREW_LIBRARY}/*.rb
-        #{HOMEBREW_LIBRARY}/Homebrew/**/*.rb
-      ]
-      Dir.glob(scan_files).each do |rb|
-        next if rb.include?("/vendor/")
-        next if rb.include?("/cask/")
-        ruby_files << rb
-      end
 
       Homebrew.failed = true unless Readall.valid_ruby_syntax?(ruby_files)
     end
@@ -31,7 +24,7 @@ module Homebrew
     taps = if ARGV.named.empty?
       Tap
     else
-      [Tap.fetch(ARGV.named.first)]
+      ARGV.named.map { |t| Tap.fetch(t) }
     end
     taps.each do |tap|
       Homebrew.failed = true unless Readall.valid_tap?(tap, options)

Library/Homebrew/cmd/search.rb

@@ -24,7 +24,7 @@ module Homebrew
 
   def search
     if ARGV.empty?
-      puts Formatter.columns(Formula.full_names)
+      puts Formatter.columns(Formula.full_names.sort)
     elsif ARGV.include? "--macports"
       exec_browser "https://www.macports.org/ports.php?by=name&substr=#{ARGV.next}"
     elsif ARGV.include? "--fink"
@@ -52,15 +52,15 @@ module Homebrew
         results = search_taps(name)
       end
 
-      puts Formatter.columns(results) unless results.empty?
+      puts Formatter.columns(results.sort) unless results.empty?
     else
       query = ARGV.first
       regex = query_regexp(query)
       local_results = search_formulae(regex)
-      puts Formatter.columns(local_results) unless local_results.empty?
+      puts Formatter.columns(local_results.sort) unless local_results.empty?
 
       tap_results = search_taps(query)
-      puts Formatter.columns(tap_results) unless tap_results.empty?
+      puts Formatter.columns(tap_results.sort) unless tap_results.empty?
 
       if $stdout.tty?
         count = local_results.length + tap_results.length
@@ -87,7 +87,7 @@ module Homebrew
         arg.include?(char) && !arg.start_with?("/")
       end
     end
-    ohai <<-EOS.undent
+    ohai <<~EOS
       Did you mean to perform a regular expression search?
       Surround your query with /slashes/ to search locally by regex.
     EOS

Library/Homebrew/cmd/sh.rb

@@ -27,14 +27,14 @@ module Homebrew
     end
     ENV["PS1"] = 'brew \[\033[1;32m\]\w\[\033[0m\]$ '
     ENV["VERBOSE"] = "1"
-    puts <<-EOS.undent_________________________________________________________72
+    puts <<~EOS
-         Your shell has been configured to use Homebrew's build environment;
+      Your shell has been configured to use Homebrew's build environment;
-         this should help you build stuff. Notably though, the system versions of
+      this should help you build stuff. Notably though, the system versions of
-         gem and pip will ignore our configuration and insist on using the
+      gem and pip will ignore our configuration and insist on using the
-         environment they were built under (mostly). Sadly, scons will also
+      environment they were built under (mostly). Sadly, scons will also
-         ignore our configuration.
+      ignore our configuration.
-         When done, type `exit'.
+      When done, type `exit'.
-         EOS
+    EOS
     $stdout.flush
     exec ENV["SHELL"]
   end

Library/Homebrew/cmd/tap-info.rb

@@ -21,10 +21,11 @@ module Homebrew
   module_function
 
   def tap_info
+    # TODO: This still returns a non-alphabetised list on APFS.
     if ARGV.include? "--installed"
       taps = Tap
     else
-      taps = ARGV.named.map do |name|
+      taps = ARGV.named.sort.map do |name|
         Tap.fetch(name)
       end
     end

Library/Homebrew/cmd/uninstall.rb

@@ -131,7 +131,7 @@ module Homebrew
 
   class DeveloperDependentsMessage < DependentsMessage
     def output
-      opoo <<-EOS.undent
+      opoo <<~EOS
         #{list reqs} #{are_required_by_deps}.
         You can silence this warning with:
           #{sample_command}
@@ -141,7 +141,7 @@ module Homebrew
 
   class NondeveloperDependentsMessage < DependentsMessage
     def output
-      ofail <<-EOS.undent
+      ofail <<~EOS
         Refusing to uninstall #{list reqs}
         because #{they reqs} #{are_required_by_deps}.
         You can override this and force removal with:

Library/Homebrew/cmd/unlinkapps.rb

@@ -20,7 +20,7 @@ module Homebrew
   module_function
 
   def unlinkapps
-    opoo <<-EOS.undent
+    opoo <<~EOS
       `brew unlinkapps` has been deprecated and will eventually be removed!
 
       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.

Library/Homebrew/cmd/update-report.rb

@@ -33,7 +33,7 @@ module Homebrew
 
         # Use an extra newline and bold to avoid this being missed.
         ohai "Homebrew has enabled anonymous aggregate user behaviour analytics."
-        puts <<-EOS.undent
+        puts <<~EOS
           #{Tty.bold}Read the analytics documentation (and how to opt-out) here:
             #{Formatter.url("https://docs.brew.sh/Analytics.html")}#{Tty.reset}
 
@@ -167,7 +167,7 @@ module Homebrew
     end
 
     if @migration_failed
-      opoo <<-EOS.undent
+      opoo <<~EOS
         Failed to migrate #{legacy_cache} to
         #{HOMEBREW_CACHE}. Please do so manually.
       EOS
@@ -176,7 +176,7 @@ module Homebrew
       FileUtils.rm_rf legacy_cache
       if legacy_cache.exist?
         FileUtils.touch migration_attempted_file
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Failed to delete #{legacy_cache}.
           Please do so manually.
         EOS
@@ -191,7 +191,7 @@ module Homebrew
     ohai "Migrating HOMEBREW_REPOSITORY (please wait)..."
 
     unless HOMEBREW_PREFIX.writable_real?
-      ofail <<-EOS.undent
+      ofail <<~EOS
         #{HOMEBREW_PREFIX} is not writable.
 
         You should change the ownership and permissions of #{HOMEBREW_PREFIX}
@@ -205,7 +205,7 @@ module Homebrew
     new_homebrew_repository = Pathname.new "/usr/local/Homebrew"
     new_homebrew_repository.rmdir_if_possible
     if new_homebrew_repository.exist?
-      ofail <<-EOS.undent
+      ofail <<~EOS
         #{new_homebrew_repository} already exists.
         Please remove it manually or uninstall and reinstall Homebrew into a new
         location as the migration cannot be done automatically.
@@ -258,7 +258,7 @@ module Homebrew
     end
 
     unless unremovable_paths.empty?
-      ofail <<-EOS.undent
+      ofail <<~EOS
         Could not remove old HOMEBREW_REPOSITORY paths!
         Please do this manually with:
           sudo rm -rf #{unremovable_paths.join " "}
@@ -274,7 +274,7 @@ module Homebrew
     begin
       FileUtils.ln_s(src.relative_path_from(dst.parent), dst)
     rescue Errno::EACCES, Errno::ENOENT
-      ofail <<-EOS.undent
+      ofail <<~EOS
         Could not create symlink at #{dst}!
         Please do this manually with:
           sudo ln -sf #{src} #{dst}
@@ -285,13 +285,13 @@ module Homebrew
     link_completions_manpages_and_docs(new_homebrew_repository)
 
     ohai "Migrated HOMEBREW_REPOSITORY to #{new_homebrew_repository}!"
-    puts <<-EOS.undent
+    puts <<~EOS
       Homebrew no longer needs to have ownership of /usr/local. If you wish you can
       return /usr/local to its default ownership with:
         sudo chown root:wheel #{HOMEBREW_PREFIX}
     EOS
   rescue => e
-    ofail <<-EOS.undent
+    ofail <<~EOS
       #{Tty.bold}Failed to migrate HOMEBREW_REPOSITORY to #{new_homebrew_repository}!#{Tty.reset}
       The error was:
         #{e}
@@ -309,7 +309,7 @@ module Homebrew
     Utils::Link.link_manpages(repository, command)
     Utils::Link.link_docs(repository, command)
   rescue => e
-    ofail <<-EOS.undent
+    ofail <<~EOS
       Failed to link all completions, docs and manpages:
         #{e}
     EOS
@@ -449,7 +449,7 @@ class Reporter
         next unless (HOMEBREW_PREFIX/"Caskroom"/new_name).exist?
         new_tap = Tap.fetch(new_tap_name)
         new_tap.install unless new_tap.installed?
-        ohai "#{name} has been moved to Homebrew.", <<-EOS.undent
+        ohai "#{name} has been moved to Homebrew.", <<~EOS
           To uninstall the cask run:
             brew cask uninstall --force #{name}
         EOS
@@ -480,14 +480,14 @@ class Reporter
           system HOMEBREW_BREW_FILE, "prune"
           ohai "brew cask install #{new_name}"
           system HOMEBREW_BREW_FILE, "cask", "install", new_name
-          ohai <<-EOS.undent
+          ohai <<~EOS
             #{name} has been moved to Homebrew-Cask.
             The existing keg has been unlinked.
             Please uninstall the formula when convenient by running:
               brew uninstall --force #{name}
           EOS
         else
-          ohai "#{name} has been moved to Homebrew-Cask.", <<-EOS.undent
+          ohai "#{name} has been moved to Homebrew-Cask.", <<~EOS
             To uninstall the formula and install the cask run:
               brew uninstall --force #{name}
               brew cask install #{new_name}
@@ -598,7 +598,7 @@ class ReporterHub
     return if formulae.empty?
     # Dump formula list.
     ohai title
-    puts Formatter.columns(formulae)
+    puts Formatter.columns(formulae.sort)
   end
 
   def installed?(formula)

Library/Homebrew/cmd/upgrade.rb

@@ -26,7 +26,7 @@ module Homebrew
     Homebrew.perform_preinstall_checks
 
     if ARGV.include?("--all")
-      opoo <<-EOS.undent
+      opoo <<~EOS
         We decided to not change the behaviour of `brew upgrade` so
         `brew upgrade --all` is equivalent to `brew upgrade` without any other
         arguments (so the `--all` is a no-op and can be removed).

Library/Homebrew/cmd/uses.rb

@@ -125,7 +125,7 @@ module Homebrew
     end
 
     return if uses.empty?
-    puts Formatter.columns(uses.map(&:full_name))
+    puts Formatter.columns(uses.map(&:full_name).sort)
     odie "Missing formulae should not have dependents!" if used_formulae_missing
   end
 end

Library/Homebrew/cmd/vendor-install.sh

@@ -21,8 +21,8 @@ then
   fi
 elif [[ -n "$HOMEBREW_LINUX" ]]
 then
-  ruby_URL="https://homebrew.bintray.com/bottles-portable/portable-ruby-2.3.3.x86_64_linux.bottle.tar.gz"
+  ruby_URL="https://homebrew.bintray.com/bottles-portable/portable-ruby-2.3.3.x86_64_linux.bottle.1.tar.gz"
-  ruby_SHA="543c18bd33a300e6c16671437b1e0f17b03bb64e6a485fc15ff7de1eb1a0bc2a"
+  ruby_SHA="33643b1ca6f860d6df01686636326785763e5e81cf0cef37d8a7ab96a6ca1fa1"
 fi
 
 fetch() {
@@ -81,9 +81,9 @@ fetch() {
     trap - SIGINT
   fi
 
-  if [[ -x "$(which shasum)" ]]
+  if [[ -x "/usr/bin/shasum" ]]
   then
-    sha="$(shasum -a 256 "$CACHED_LOCATION" | cut -d' ' -f1)"
+    sha="$(/usr/bin/shasum -a 256 "$CACHED_LOCATION" | cut -d' ' -f1)"
   elif [[ -x "$(which sha256sum)" ]]
   then
     sha="$(sha256sum "$CACHED_LOCATION" | cut -d' ' -f1)"

Library/Homebrew/compat.rb

@@ -26,3 +26,4 @@ require "compat/ENV/shared"
 require "compat/ENV/std"
 require "compat/ENV/super"
 require "compat/utils/shell"
+require "compat/extend/string"

Library/Homebrew/compat/extend/string.rb

@@ -0,0 +1,18 @@
+class String
+  def undent
+    gsub(/^[ \t]{#{(slice(/^[ \t]+/) || '').length}}/, "")
+  end
+  alias unindent undent
+
+  # eg:
+  #   if foo then <<-EOS.undent_________________________________________________________72
+  #               Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do
+  #               eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
+  #               minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip
+  #               ex ea commodo consequat. Duis aute irure dolor in reprehenderit in
+  #               voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur
+  #               sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt
+  #               mollit anim id est laborum.
+  #               EOS
+  alias undent_________________________________________________________72 undent
+end

Library/Homebrew/compat/formula_specialties.rb

@@ -31,7 +31,7 @@ class AmazonWebServicesFormula < Formula
   def standard_instructions(home_name, home_value = libexec)
     odeprecated "AmazonWebServicesFormula#standard_instructions", "Formula#caveats"
 
-    <<-EOS.undent
+    <<~EOS
       Before you can use these tools you must export some variables to your $SHELL.
 
       To export the needed variables, add them to your dotfiles.

Library/Homebrew/compat/hbc/cli.rb

@@ -5,7 +5,7 @@ module Hbc
     include Options
 
     option "--binarydir=PATH", (lambda do |*|
-      opoo <<-EOS.undent
+      opoo <<~EOS
         Option --binarydir is obsolete!
         Homebrew-Cask now uses the same location as your Homebrew installation for executable links.
       EOS

Library/Homebrew/compat/requirements.rb

@@ -17,3 +17,4 @@ PythonDependency           = PythonRequirement
 TuntapDependency           = TuntapRequirement
 X11Dependency              = X11Requirement
 ConflictsWithBinaryOsxfuse = NonBinaryOsxfuseRequirement
+MinimumMacOSRequirement    = MacOSRequirement

Library/Homebrew/constants.rb

@@ -2,4 +2,4 @@
 
 # RuboCop version used for `brew style` and `brew cask style`
 HOMEBREW_RUBOCOP_VERSION = "0.50.0"
-HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.14.2" # has to be updated when RuboCop version changes
+HOMEBREW_RUBOCOP_CASK_VERSION = "~> 0.14.4" # has to be updated when RuboCop version changes

Library/Homebrew/cxxstdlib.rb

@@ -5,7 +5,7 @@ class CxxStdlib
 
   class CompatibilityError < StandardError
     def initialize(formula, dep, stdlib)
-      super <<-EOS.undent
+      super <<~EOS
         #{formula.full_name} dependency #{dep.name} was built with a different C++ standard
         library (#{stdlib.type_string} from #{stdlib.compiler}). This may cause problems at runtime.
         EOS

Library/Homebrew/dependency_collector.rb

@@ -105,7 +105,8 @@ class DependencyCollector
     case spec
     when :x11        then X11Requirement.new(spec.to_s, tags)
     when :xcode      then XcodeRequirement.new(tags)
-    when :macos      then MinimumMacOSRequirement.new(tags)
+    when :linux      then LinuxRequirement.new(tags)
+    when :macos      then MacOSRequirement.new(tags)
     when :mysql      then MysqlRequirement.new(tags)
     when :postgresql then PostgresqlRequirement.new(tags)
     when :gpg        then GPG2Requirement.new(tags)

Library/Homebrew/dev-cmd/audit.rb

@@ -368,7 +368,7 @@ class FormulaAuditor
 
       if valid_versioned_aliases.empty?
         if formula.tap
-          problem <<-EOS.undent
+          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}
@@ -379,7 +379,7 @@ class FormulaAuditor
       end
 
       unless invalid_versioned_aliases.empty?
-        problem <<-EOS.undent
+        problem <<~EOS
           Formula has invalid versioned aliases:
             #{invalid_versioned_aliases.join("\n  ")}
         EOS
@@ -476,7 +476,7 @@ class FormulaAuditor
         when "gfortran"
           problem "Use `depends_on :fortran` instead of `depends_on 'gfortran'`"
         when "ruby"
-          problem <<-EOS.undent
+          problem <<~EOS
             Don't use "ruby" as a dependency. If this formula requires a
             minimum Ruby version not provided by the system you should
             use the RubyRequirement:
@@ -484,7 +484,7 @@ class FormulaAuditor
             where "1.8" is the minimum version of Ruby required.
           EOS
         when "open-mpi", "mpich"
-          problem <<-EOS.undent
+          problem <<~EOS
             There are multiple conflicting ways to install MPI. Use an MPIRequirement:
               depends_on :mpi => [<lang list>]
             Where <lang list> is a comma delimited list that can include:
@@ -492,7 +492,7 @@ class FormulaAuditor
             EOS
         when *BUILD_TIME_DEPS
           next if dep.build? || dep.run?
-          problem <<-EOS.undent
+          problem <<~EOS
             #{dep} dependency should be
               depends_on "#{dep}" => :build
             Or if it is indeed a runtime dependency
@@ -541,7 +541,7 @@ class FormulaAuditor
     first_word = reason.split[0]
 
     if reason =~ /\A[A-Z]/ && !reason.start_with?(*whitelist)
-      problem <<-EOS.undent
+      problem <<~EOS
         '#{first_word}' from the keg_only reason should be '#{first_word.downcase}'.
       EOS
     end
@@ -854,7 +854,7 @@ class FormulaAuditor
     return unless formula.tap&.official?
     return unless formula.tap.tap_migrations.key?(formula.name)
 
-    problem <<-EOS.undent
+    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}.
@@ -865,7 +865,7 @@ class FormulaAuditor
     return unless formula.prefix.directory?
     return unless Keg.new(formula.prefix).empty_installation?
 
-    problem <<-EOS.undent
+    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.

Library/Homebrew/dev-cmd/bottle.rb

@@ -324,7 +324,7 @@ module Homebrew
           "#{key}: old: #{old_value}, new: #{value}"
         end
 
-        odie <<-EOS.undent
+        odie <<~EOS
           --keep-old was passed but there are changes in:
           #{mismatches.join("\n")}
         EOS
@@ -428,7 +428,7 @@ module Homebrew
               end
 
               unless mismatches.empty?
-                odie <<-EOS.undent
+                odie <<~EOS
                   --keep-old was passed but there are changes in:
                   #{mismatches.join("\n")}
                 EOS

Library/Homebrew/dev-cmd/bump-formula-pr.rb

@@ -91,7 +91,7 @@ module Homebrew
     pull_requests = fetch_pull_requests(formula)
     return unless pull_requests
     return if pull_requests.empty?
-    duplicates_message = <<-EOS.undent
+    duplicates_message = <<~EOS
       These open pull requests may be duplicates:
       #{pull_requests.map { |pr| "#{pr["title"]} #{pr["html_url"]}" }.join("\n")}
     EOS
@@ -101,7 +101,7 @@ module Homebrew
     elsif !ARGV.force? && ARGV.flag?("--quiet")
       odie error_message
     elsif !ARGV.force?
-      odie <<-EOS.undent
+      odie <<~EOS
         #{duplicates_message.chomp}
         #{error_message}
       EOS
@@ -247,13 +247,13 @@ module Homebrew
 
     if new_formula_version < old_formula_version
       formula.path.atomic_write(backup_file) unless ARGV.dry_run?
-      odie <<-EOS.undent
+      odie <<~EOS
         You probably need to bump this formula manually since changing the
         version from #{old_formula_version} to #{new_formula_version} would be a downgrade.
       EOS
     elsif new_formula_version == old_formula_version
       formula.path.atomic_write(backup_file) unless ARGV.dry_run?
-      odie <<-EOS.undent
+      odie <<~EOS
         You probably need to bump this formula manually since the new version
         and old version are both #{new_formula_version}.
       EOS
@@ -312,17 +312,15 @@ module Homebrew
         remote = Utils.popen_read("hub fork 2>&1")[/remote:? (\S+)/, 1] if remote.to_s.empty?
         odie "cannot get remote from 'hub'!" if remote.to_s.empty?
         safe_system "git", "push", "--set-upstream", remote, "#{branch}:#{branch}"
-        pr_message = <<-EOS.undent
+        pr_message = <<~EOS
           #{formula.name} #{new_formula_version}#{devel_message}
 
           Created with `brew bump-formula-pr`.
         EOS
         user_message = ARGV.value("message")
         if user_message
-          pr_message += <<-EOS.undent
+          pr_message += <<~EOS
-
             ---
-
             #{user_message}
           EOS
         end

Library/Homebrew/dev-cmd/create.rb

@@ -71,7 +71,7 @@ module Homebrew
 
       if Formula.aliases.include? fc.name
         realname = Formulary.canonical_name(fc.name)
-        raise <<-EOS.undent
+        raise <<~EOS
           The formula #{realname} is already aliased to #{fc.name}
           Please check that you are not creating a duplicate.
           To force creation use --force.
@@ -165,7 +165,7 @@ class FormulaCreator
     path.write ERB.new(template, nil, ">").result(binding)
   end
 
-  def template; <<-EOS.undent
+  def template; <<~EOS
     # Documentation: https://docs.brew.sh/Formula-Cookbook.html
     #                http://www.rubydoc.info/github/Homebrew/brew/master/Formula
     # PLEASE REMOVE ALL GENERATED COMMENTS BEFORE SUBMITTING YOUR PULL REQUEST!

Library/Homebrew/dev-cmd/edit.rb

@@ -11,7 +11,7 @@ module Homebrew
 
   def edit
     unless (HOMEBREW_REPOSITORY/".git").directory?
-      raise <<-EOS.undent
+      raise <<~EOS
         Changes will be lost!
         The first time you `brew update', all local changes will be lost, you should
         thus `brew update' before you `brew edit'!

Library/Homebrew/dev-cmd/mirror.rb

@@ -20,7 +20,7 @@ module Homebrew
       package_url = "#{bintray_repo_url}/#{bintray_package}"
 
       unless system "curl", "--silent", "--fail", "--output", "/dev/null", package_url
-        package_blob = <<-EOS.undent
+        package_blob = <<~EOS
           {"name": "#{bintray_package}",
            "public_download_numbers": true,
            "public_stats": true}

Library/Homebrew/dev-cmd/pull.rb

@@ -1,4 +1,4 @@
-#:  * `pull` [`--bottle`] [`--bump`] [`--clean`] [`--ignore-whitespace`] [`--resolve`] [`--branch-okay`] [`--no-pbcopy`] [`--no-publish`] [`--warn-on-publish-failure`] <patch-source> [<patch-source>]:
+#:  * `pull` [`--bottle`] [`--bump`] [`--clean`] [`--ignore-whitespace`] [`--resolve`] [`--branch-okay`] [`--no-pbcopy`] [`--no-publish`] [`--warn-on-publish-failure`] [`--bintray-org=`<bintray-org>] [`--test-bot-user=`<test-bot-user>] <patch-source> [<patch-source>]:
 #:
 #:    Gets a patch from a GitHub commit or pull request and applies it to Homebrew.
 #:    Optionally, installs the formulae changed by the patch.
@@ -41,6 +41,12 @@
 #:
 #:    If `--warn-on-publish-failure` was passed, do not exit if there's a
 #:    failure publishing bottles on Bintray.
+#:
+#:    If `--bintray-org=`<bintray-org> is passed, publish at the given Bintray
+#:    organisation.
+#:
+#:    If `--test-bot-user=`<test-bot-user> is passed, pull the bottle block
+#:    commit from the specified user on GitHub.
 
 require "net/http"
 require "net/https"
@@ -52,6 +58,18 @@ require "tap"
 require "version"
 require "pkg_version"
 
+module GitHub
+  module_function
+
+  # Return the corresponding test-bot user name for the given GitHub organization.
+  def test_bot_user(user)
+    test_bot = ARGV.value "test-bot-user"
+    return test_bot if test_bot
+    return "BrewTestBot" if user.casecmp("homebrew").zero?
+    "#{user.capitalize}TestBot"
+  end
+end
+
 module Homebrew
   module_function
 
@@ -225,7 +243,7 @@ module Homebrew
           url
         else
           bottle_branch = "pull-bottle-#{issue}"
-          "https://github.com/BrewTestBot/homebrew-#{tap.repo}/compare/homebrew:master...pr-#{issue}"
+          "https://github.com/#{GitHub.test_bot_user user}/homebrew-#{tap.repo}/compare/#{user}:master...pr-#{issue}"
         end
 
         curl "--silent", "--fail", "--output", "/dev/null", "--head", bottle_commit_url
@@ -257,7 +275,7 @@ module Homebrew
     str.force_encoding("UTF-8") if str.respond_to?(:force_encoding)
   end
 
-  def publish_changed_formula_bottles(_tap, changed_formulae_names)
+  def publish_changed_formula_bottles(tap, changed_formulae_names)
     if ENV["HOMEBREW_DISABLE_LOAD_FORMULA"]
       raise "Need to load formulae to publish them!"
     end
@@ -268,7 +286,8 @@ module Homebrew
       changed_formulae_names.each do |name|
         f = Formula[name]
         next if f.bottle_unneeded? || f.bottle_disabled?
-        next unless publish_bottle_file_on_bintray(f, bintray_creds)
+        bintray_org = ARGV.value("bintray-org") || tap.user.downcase
+        next unless publish_bottle_file_on_bintray(f, bintray_org, bintray_creds)
         published << f.full_name
       end
     else
@@ -420,7 +439,7 @@ module Homebrew
   end
 
   # Publishes the current bottle files for a given formula to Bintray
-  def publish_bottle_file_on_bintray(f, creds)
+  def publish_bottle_file_on_bintray(f, bintray_org, creds)
     repo = Utils::Bottles::Bintray.repository(f.tap)
     package = Utils::Bottles::Bintray.package(f.name)
     info = FormulaInfoFromJson.lookup(f.name)
@@ -437,7 +456,7 @@ module Homebrew
          "--user", "#{creds[:user]}:#{creds[:key]}", "--request", "POST",
          "--header", "Content-Type: application/json",
          "--data", '{"publish_wait_for_secs": 0}',
-         "https://api.bintray.com/content/homebrew/#{repo}/#{package}/#{version}/publish"
+         "https://api.bintray.com/content/#{bintray_org}/#{repo}/#{package}/#{version}/publish"
     true
   rescue => e
     raise unless ARGV.include?("--warn-on-publish-failure")

Library/Homebrew/dev-cmd/tap-new.rb

@@ -24,7 +24,7 @@ module Homebrew
 
     (tap.path/"Formula").mkpath
 
-    readme = <<-EOS.undent
+    readme = <<~EOS
       # #{titleized_user} #{titleized_repo}
 
       ## How do I install these formulae?
@@ -43,7 +43,7 @@ module Homebrew
     EOS
     write_path(tap, "README.md", readme)
 
-    travis = <<-EOS.undent
+    travis = <<~EOS
       language: ruby
       os: osx
       env: OSX=10.12

Library/Homebrew/dev-cmd/update-test.rb

@@ -88,7 +88,7 @@ module Homebrew
       safe_system "brew", "update", "--verbose"
       actual_end_commit = Utils.popen_read("git", "rev-parse", branch).chomp
       if start_commit != end_commit && start_commit == actual_end_commit
-        raise <<-EOS.undent
+        raise <<~EOS
           brew update didn't update #{branch}!
           Start commit:        #{start_commit}
           Expected end commit: #{end_commit}

Library/Homebrew/diagnostic.rb

@@ -92,7 +92,7 @@ module Homebrew
       def check_for_installed_developer_tools
         return if DevelopmentTools.installed?
 
-        <<-EOS.undent
+        <<~EOS
           No developer tools installed.
           #{DevelopmentTools.installation_instructions}
         EOS
@@ -101,7 +101,7 @@ module Homebrew
       def check_build_from_source
         return unless ENV["HOMEBREW_BUILD_FROM_SOURCE"]
 
-        <<-EOS.undent
+        <<~EOS
           You have HOMEBREW_BUILD_FROM_SOURCE set. This environment variable is
           intended for use by Homebrew developers. If you are encountering errors,
           please try unsetting this. Please do not file issues if you encounter
@@ -114,7 +114,7 @@ module Homebrew
         bad_paths = PATH.new(ENV["HOMEBREW_PATH"]).select { |p| p.end_with?("/") }
         return if bad_paths.empty?
 
-        inject_file_list bad_paths, <<-EOS.undent
+        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:
@@ -136,7 +136,7 @@ module Homebrew
         # Only warn if Python lives with Anaconda, since is most problematic case.
         return unless python_directory == anaconda_directory
 
-        <<-EOS.undent
+        <<~EOS
           Anaconda is known to frequently break Homebrew builds, including Vim and
           MacVim, due to bundling many duplicates of system and Homebrew-available
           tools.
@@ -182,7 +182,7 @@ module Homebrew
           "sentinel.dylib", # SentinelOne
         ]
 
-        __check_stray_files "/usr/local/lib", "*.dylib", white_list, <<-EOS.undent
+        __check_stray_files "/usr/local/lib", "*.dylib", white_list, <<~EOS
           Unbrewed dylibs were found in /usr/local/lib.
           If you didn't put them there on purpose they could cause problems when
           building Homebrew formulae, and may need to be deleted.
@@ -209,7 +209,7 @@ module Homebrew
           "libtrustedcomponents.a", # Symantec Endpoint Protection
         ]
 
-        __check_stray_files "/usr/local/lib", "*.a", white_list, <<-EOS.undent
+        __check_stray_files "/usr/local/lib", "*.a", white_list, <<~EOS
           Unbrewed static libraries were found in /usr/local/lib.
           If you didn't put them there on purpose they could cause problems when
           building Homebrew formulae, and may need to be deleted.
@@ -229,7 +229,7 @@ module Homebrew
           "libublio.pc", # NTFS-3G
         ]
 
-        __check_stray_files "/usr/local/lib/pkgconfig", "*.pc", white_list, <<-EOS.undent
+        __check_stray_files "/usr/local/lib/pkgconfig", "*.pc", white_list, <<~EOS
           Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
           If you didn't put them there on purpose they could cause problems when
           building Homebrew formulae, and may need to be deleted.
@@ -250,7 +250,7 @@ module Homebrew
           "libublio.la", # NTFS-3G
         ]
 
-        __check_stray_files "/usr/local/lib", "*.la", white_list, <<-EOS.undent
+        __check_stray_files "/usr/local/lib", "*.la", white_list, <<~EOS
           Unbrewed .la files were found in /usr/local/lib.
           If you didn't put them there on purpose they could cause problems when
           building Homebrew formulae, and may need to be deleted.
@@ -269,7 +269,7 @@ module Homebrew
           "ntfs-3g/**/*.h", # NTFS-3G
         ]
 
-        __check_stray_files "/usr/local/include", "**/*.h", white_list, <<-EOS.undent
+        __check_stray_files "/usr/local/include", "**/*.h", white_list, <<~EOS
           Unbrewed header files were found in /usr/local/include.
           If you didn't put them there on purpose they could cause problems when
           building Homebrew formulae, and may need to be deleted.
@@ -291,7 +291,7 @@ module Homebrew
         end
         return if broken_symlinks.empty?
 
-        inject_file_list broken_symlinks, <<-EOS.undent
+        inject_file_list broken_symlinks, <<~EOS
           Broken symlinks were found. Remove them with `brew prune`:
         EOS
       end
@@ -300,7 +300,7 @@ module Homebrew
         world_writable = HOMEBREW_TEMP.stat.mode & 0777 == 0777
         return if !world_writable || HOMEBREW_TEMP.sticky?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_TEMP} is world-writable but does not have the sticky bit set.
           Please execute `sudo chmod +t #{HOMEBREW_TEMP}` in your Terminal.
         EOS
@@ -309,7 +309,7 @@ module Homebrew
       def check_access_homebrew_repository
         return if HOMEBREW_REPOSITORY.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_REPOSITORY} is not writable.
 
           You should change the ownership and permissions of #{HOMEBREW_REPOSITORY}
@@ -330,7 +330,7 @@ module Homebrew
 
         return if not_writable_dirs.empty?
 
-        <<-EOS.undent
+        <<~EOS
           The following directories are not writable:
           #{not_writable_dirs.join("\n")}
 
@@ -348,7 +348,7 @@ module Homebrew
         return unless Language::Python.homebrew_site_packages.exist?
         return if Language::Python.homebrew_site_packages.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{Language::Python.homebrew_site_packages} isn't writable.
           This can happen if you "sudo pip install" software that isn't managed
           by Homebrew. If you install a formula with Python modules, the install
@@ -364,7 +364,7 @@ module Homebrew
         return unless HOMEBREW_LOCK_DIR.exist?
         return if HOMEBREW_LOCK_DIR.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_LOCK_DIR} isn't writable.
           Homebrew writes lock files to this location.
 
@@ -378,7 +378,7 @@ module Homebrew
         return unless HOMEBREW_LOGS.exist?
         return if HOMEBREW_LOGS.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_LOGS} isn't writable.
           Homebrew writes debugging logs to this location.
 
@@ -392,7 +392,7 @@ module Homebrew
         return unless HOMEBREW_CACHE.exist?
         return if HOMEBREW_CACHE.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_CACHE} isn't writable.
           This can happen if you run `brew install` or `brew fetch` as another user.
           Homebrew caches downloaded files to this location.
@@ -407,7 +407,7 @@ module Homebrew
         return unless HOMEBREW_CELLAR.exist?
         return if HOMEBREW_CELLAR.writable_real?
 
-        <<-EOS.undent
+        <<~EOS
           #{HOMEBREW_CELLAR} isn't writable.
 
           You should change the ownership and permissions of #{HOMEBREW_CELLAR}
@@ -421,7 +421,7 @@ module Homebrew
         return unless (HOMEBREW_REPOSITORY/"Cellar").exist?
         return unless (HOMEBREW_PREFIX/"Cellar").exist?
 
-        <<-EOS.undent
+        <<~EOS
           You have multiple Cellars.
           You should delete #{HOMEBREW_REPOSITORY}/Cellar:
             rm -rf #{HOMEBREW_REPOSITORY}/Cellar
@@ -445,13 +445,13 @@ module Homebrew
                           .select { |bn| File.exist? "/usr/bin/#{bn}" }
 
               unless conflicts.empty?
-                message = inject_file_list conflicts, <<-EOS.undent
+                message = inject_file_list conflicts, <<~EOS
                   /usr/bin occurs before #{HOMEBREW_PREFIX}/bin
                   This means that system-provided programs will be used instead of those
                   provided by Homebrew. The following tools exist at both paths:
                 EOS
 
-                message += <<-EOS.undent
+                message += <<~EOS
 
                   Consider setting your PATH so that #{HOMEBREW_PREFIX}/bin
                   occurs before /usr/bin. Here is a one-liner:
@@ -472,7 +472,7 @@ module Homebrew
       def check_user_path_2
         return if @seen_prefix_bin
 
-        <<-EOS.undent
+        <<~EOS
           Homebrew's bin was not found in your PATH.
           Consider setting the PATH for example like so
             #{Utils::Shell.prepend_path_in_profile("#{HOMEBREW_PREFIX}/bin")}
@@ -486,7 +486,7 @@ module Homebrew
         sbin = HOMEBREW_PREFIX/"sbin"
         return unless sbin.directory? && !sbin.children.empty?
 
-        <<-EOS.undent
+        <<~EOS
           Homebrew's sbin was not found in your PATH but you have installed
           formulae that put executables in #{HOMEBREW_PREFIX}/sbin.
           Consider setting the PATH for example like so
@@ -500,7 +500,7 @@ module Homebrew
         end
         return unless curlrc_found
 
-        <<-EOS.undent
+        <<~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
@@ -526,7 +526,7 @@ module Homebrew
         end
         return if gettext&.linked_keg&.directory? && homebrew_owned
 
-        inject_file_list @found, <<-EOS.undent
+        inject_file_list @found, <<~EOS
           gettext files detected at a system prefix.
           These files can cause compilation and link failures, especially if they
           are compiled with improper architectures. Consider removing these files:
@@ -544,13 +544,13 @@ module Homebrew
         end
         if libiconv&.linked_keg&.directory?
           unless libiconv.keg_only?
-            <<-EOS.undent
+            <<~EOS
               A libiconv formula is installed and linked.
               This will break stuff. For serious. Unlink it.
             EOS
           end
         else
-          inject_file_list @found, <<-EOS.undent
+          inject_file_list @found, <<~EOS
             libiconv files detected at a system prefix other than /usr.
             Homebrew doesn't provide a libiconv formula, and expects to link against
             the system version in /usr. libiconv in other prefixes can cause
@@ -588,7 +588,7 @@ module Homebrew
 
         return if scripts.empty?
 
-        inject_file_list scripts, <<-EOS.undent
+        inject_file_list scripts, <<~EOS
           "config" scripts exist outside your system or Homebrew directories.
           `./configure` scripts often look for *-config scripts to determine if
           software packages are installed, and what additional flags to use when
@@ -605,13 +605,13 @@ module Homebrew
         return if dyld_vars.empty?
 
         values = dyld_vars.map { |var| "#{var}: #{ENV.fetch(var)}" }
-        message = inject_file_list values, <<-EOS.undent
+        message = inject_file_list values, <<~EOS
           Setting DYLD_* vars can break dynamic linking.
           Set variables:
         EOS
 
         if dyld_vars.include? "DYLD_INSERT_LIBRARIES"
-          message += <<-EOS.undent
+          message += <<~EOS
 
             Setting DYLD_INSERT_LIBRARIES can cause Go builds to fail.
             Having this set is common if you use this software:
@@ -624,7 +624,7 @@ module Homebrew
 
       def check_ssl_cert_file
         return unless ENV.key?("SSL_CERT_FILE")
-        <<-EOS.undent
+        <<~EOS
           Setting SSL_CERT_FILE can break downloading files; if that happens
           you should unset it before running Homebrew.
 
@@ -638,7 +638,7 @@ module Homebrew
         return unless HOMEBREW_CELLAR.exist?
         return unless HOMEBREW_CELLAR.symlink?
 
-        <<-EOS.undent
+        <<~EOS
           Symlinked Cellars can cause problems.
           Your Homebrew Cellar is a symlink: #{HOMEBREW_CELLAR}
                           which resolves to: #{HOMEBREW_CELLAR.realpath}
@@ -675,7 +675,7 @@ module Homebrew
 
         return if where_cellar == where_tmp
 
-        <<-EOS.undent
+        <<~EOS
           Your Cellar and TEMP directories are on different volumes.
           macOS won't move relative symlinks across volumes unless the target file already
           exists. Brews known to be affected by this are Git and Narwhal.
@@ -692,7 +692,7 @@ module Homebrew
 
         git = Formula["git"]
         git_upgrade_cmd = git.any_version_installed? ? "upgrade" : "install"
-        <<-EOS.undent
+        <<~EOS
           An outdated version (#{Utils.git_version}) of Git was detected in your PATH.
           Git 1.8.5 or newer is required to perform checkouts over HTTPS from GitHub and
           to support the 'git -C <path>' option.
@@ -704,7 +704,7 @@ module Homebrew
       def check_for_git
         return if Utils.git_available?
 
-        <<-EOS.undent
+        <<~EOS
           Git could not be found in your PATH.
           Homebrew uses Git for several internal functions, and some formulae use Git
           checkouts instead of stable tarballs. You may want to install Git:
@@ -718,7 +718,7 @@ module Homebrew
         autocrlf = HOMEBREW_REPOSITORY.cd { `git config --get core.autocrlf`.chomp }
         return unless autocrlf == "true"
 
-        <<-EOS.undent
+        <<~EOS
           Suspicious Git newline settings found.
 
           The detected Git newline settings will cause checkout problems:
@@ -736,7 +736,7 @@ module Homebrew
         origin = HOMEBREW_REPOSITORY.git_origin
 
         if origin.nil?
-          <<-EOS.undent
+          <<~EOS
             Missing Homebrew/brew git origin remote.
 
             Without a correctly configured origin, Homebrew won't update
@@ -744,7 +744,7 @@ module Homebrew
               git -C "#{HOMEBREW_REPOSITORY}" remote add origin #{Formatter.url("https://github.com/Homebrew/brew.git")}
           EOS
         elsif origin !~ %r{Homebrew/brew(\.git|/)?$}
-          <<-EOS.undent
+          <<~EOS
             Suspicious Homebrew/brew git origin remote found.
 
             With a non-standard origin, Homebrew won't pull updates from
@@ -765,7 +765,7 @@ module Homebrew
         origin = coretap_path.git_origin
 
         if origin.nil?
-          <<-EOS.undent
+          <<~EOS
             Missing #{CoreTap.instance} git origin remote.
 
             Without a correctly configured origin, Homebrew won't update
@@ -775,7 +775,7 @@ module Homebrew
         elsif origin !~ %r{Homebrew/homebrew-core(\.git|/)?$}
           return if ENV["CI"] && origin.include?("Homebrew/homebrew-test-bot")
 
-          <<-EOS.undent
+          <<~EOS
             Suspicious #{CoreTap.instance} git origin remote found.
 
             With a non-standard origin, Homebrew won't pull updates from
@@ -787,6 +787,18 @@ module Homebrew
               git -C "#{coretap_path}" remote set-url origin #{Formatter.url("https://github.com/Homebrew/homebrew-core.git")}
           EOS
         end
+
+        return if ENV["CI"] || ENV["JENKINS_HOME"]
+
+        branch = coretap_path.git_branch
+        return if branch.nil? || branch =~ /master/
+
+        <<~EOS
+          Homebrew/homebrew-core is not on the master branch
+
+          Check out the master branch by running:
+            git -C "$(brew --repo homebrew/core)" checkout master
+        EOS
       end
 
       def __check_linked_brew(f)
@@ -804,12 +816,12 @@ module Homebrew
       def check_for_linked_keg_only_brews
         return unless HOMEBREW_CELLAR.exist?
 
-        linked = Formula.installed.select do |f|
+        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.undent
+        inject_file_list linked.map(&:full_name), <<~EOS
           Some keg-only formula 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
@@ -835,7 +847,7 @@ module Homebrew
                            .select { |framework| File.exist? framework }
         return if frameworks_found.empty?
 
-        inject_file_list frameworks_found, <<-EOS.undent
+        inject_file_list frameworks_found, <<~EOS
           Some frameworks can be picked up by CMake's build system and likely
           cause the build to fail. To compile CMake, you may wish to move these
           out of the way:
@@ -846,7 +858,7 @@ module Homebrew
         tmpdir = ENV["TMPDIR"]
         return if tmpdir.nil? || File.directory?(tmpdir)
 
-        <<-EOS.undent
+        <<~EOS
           TMPDIR #{tmpdir.inspect} doesn't exist.
         EOS
       end
@@ -859,7 +871,7 @@ module Homebrew
         end
         return if missing.empty?
 
-        <<-EOS.undent
+        <<~EOS
           Some installed formula are missing dependencies.
           You should `brew install` the missing dependencies:
             brew install #{missing.sort_by(&:full_name) * " "}
@@ -874,7 +886,7 @@ module Homebrew
           return if `git status --untracked-files=all --porcelain -- Library/Homebrew/ 2>/dev/null`.chomp.empty?
         end
 
-        <<-EOS.undent
+        <<~EOS
           You have uncommitted modifications to Homebrew
           If this is a surprise to you, then you should stash these modifications.
           Stashing returns Homebrew to a pristine state but can be undone
@@ -886,7 +898,7 @@ module Homebrew
       def check_for_enthought_python
         return unless which "enpkg"
 
-        <<-EOS.undent
+        <<~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
@@ -897,7 +909,7 @@ module Homebrew
       def check_for_library_python
         return unless File.exist?("/Library/Frameworks/Python.framework")
 
-        <<-EOS.undent
+        <<~EOS
           Python is installed at /Library/Frameworks/Python.framework
 
           Homebrew only supports building against the System-provided Python or a
@@ -910,12 +922,12 @@ module Homebrew
         message = ""
         ["", "3"].map do |suffix|
           next unless paths.include?((HOMEBREW_PREFIX/"share/python#{suffix}").to_s)
-          message += <<-EOS.undent
+          message += <<~EOS
-              #{HOMEBREW_PREFIX}/share/python#{suffix} is not needed in PATH.
+            #{HOMEBREW_PREFIX}/share/python#{suffix} is not needed in PATH.
           EOS
         end
         unless message.empty?
-          message += <<-EOS.undent
+          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
@@ -937,7 +949,7 @@ module Homebrew
         return if Regexp.last_match(1).nil?
         return if Regexp.last_match(1) == "2"
 
-        <<-EOS.undent
+        <<~EOS
           python is symlinked to python#{Regexp.last_match(1)}
           This will confuse build scripts and in general lead to subtle breakage.
         EOS
@@ -950,7 +962,7 @@ module Homebrew
         gnubin = %W[#{coreutils.opt_libexec}/gnubin #{coreutils.libexec}/gnubin]
         return if (paths & gnubin).empty?
 
-        <<-EOS.undent
+        <<~EOS
           Putting non-prefixed coreutils in your path can cause gmp builds to fail.
         EOS
       rescue FormulaUnavailableError
@@ -965,7 +977,7 @@ module Homebrew
         default_names = Tab.for_name("findutils").with? "default-names"
         return if !default_names && (paths & gnubin).empty?
 
-        <<-EOS.undent
+        <<~EOS
           Putting non-prefixed findutils in your path can cause python builds to fail.
         EOS
       rescue FormulaUnavailableError
@@ -975,7 +987,7 @@ module Homebrew
       def check_for_pydistutils_cfg_in_home
         return unless File.exist? "#{ENV["HOME"]}/.pydistutils.cfg"
 
-        <<-EOS.undent
+        <<~EOS
           A .pydistutils.cfg file was found in $HOME, which may cause Python
           builds to fail. See:
             #{Formatter.url("https://bugs.python.org/issue6138")}
@@ -997,7 +1009,7 @@ module Homebrew
         end.map(&:basename)
         return if unlinked.empty?
 
-        inject_file_list unlinked, <<-EOS.undent
+        inject_file_list unlinked, <<~EOS
           You have unlinked kegs in your Cellar
           Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
           those kegs to fail to run properly once built. Run `brew link` on these:
@@ -1007,7 +1019,7 @@ module Homebrew
       def check_for_old_env_vars
         return unless ENV["HOMEBREW_KEEP_INFO"]
 
-        <<-EOS.undent
+        <<~EOS
           `HOMEBREW_KEEP_INFO` is no longer used
           info files are no longer deleted by default; you may
           remove this environment variable.
@@ -1021,7 +1033,7 @@ module Homebrew
         return unless Language::Python.in_sys_path?("python", homebrew_site_packages)
 
         user_site_packages = Language::Python.user_site_packages "python"
-        <<-EOS.undent
+        <<~EOS
           Your default Python does not recognize the Homebrew site-packages
           directory as a special site-packages directory, which means that .pth
           files will not be followed. This means you will not be able to import
@@ -1051,8 +1063,7 @@ module Homebrew
 
         message = "You have external commands with conflicting names.\n"
         cmd_map.each do |cmd_name, cmd_paths|
-          message += inject_file_list cmd_paths, <<-EOS.undent
+          message += inject_file_list cmd_paths, <<~EOS
-
             Found command `#{cmd_name}` in following places:
           EOS
         end
@@ -1075,7 +1086,7 @@ module Homebrew
         end
         return if bad_tap_files.empty?
         bad_tap_files.keys.map do |tap|
-          <<-EOS.undent
+          <<~EOS
             Found Ruby file outside #{tap} tap formula directory
             (#{tap.formula_dir}):
               #{bad_tap_files[tap].join("\n  ")}

Library/Homebrew/download_strategy.rb

@@ -159,7 +159,7 @@ class VCSDownloadStrategy < AbstractDownloadStrategy
     return unless @ref_type == :tag
     return unless @revision && current_revision
     return if current_revision == @revision
-    raise <<-EOS.undent
+    raise <<~EOS
       #{@ref} tag should be #{@revision}
       but is actually #{current_revision}
     EOS
@@ -553,9 +553,9 @@ class GitHubPrivateRepositoryDownloadStrategy < CurlDownloadStrategy
   rescue GitHub::HTTPNotFoundError
     # We only handle HTTPNotFoundError here,
     # becase AuthenticationFailedError is handled within util/github.
-    message = <<-EOS.undent
+    message = <<~EOS
-        HOMEBREW_GITHUB_API_TOKEN can not access the repository: #{@owner}/#{@repo}
+      HOMEBREW_GITHUB_API_TOKEN can not access the repository: #{@owner}/#{@repo}
-        This token may not have permission to access the repository or the url of formula may be incorrect.
+      This token may not have permission to access the repository or the url of formula may be incorrect.
     EOS
     raise CurlDownloadStrategyError, message
   end

Library/Homebrew/exceptions.rb

@@ -185,7 +185,7 @@ class TapFormulaAmbiguityError < RuntimeError
       "#{Tap.fetch(match[:user], match[:repo])}/#{path.basename(".rb")}"
     end
 
-    super <<-EOS.undent
+    super <<~EOS
       Formulae found in multiple taps: #{formulae.map { |f| "\n       * #{f}" }.join}
 
       Please use the fully-qualified name e.g. #{formulae.first} to refer the formula.
@@ -205,7 +205,7 @@ class TapFormulaWithOldnameAmbiguityError < RuntimeError
       "#{Regexp.last_match(1)}/#{Regexp.last_match(2)}"
     end
 
-    super <<-EOS.undent
+    super <<~EOS
       Formulae with '#{name}' old name found in multiple taps: #{taps.map { |t| "\n       * #{t}" }.join}
 
       Please use the fully-qualified name e.g. #{taps.first}/#{name} to refer the formula or use its new name.
@@ -219,7 +219,7 @@ class TapUnavailableError < RuntimeError
   def initialize(name)
     @name = name
 
-    super <<-EOS.undent
+    super <<~EOS
       No available tap #{name}.
     EOS
   end
@@ -235,7 +235,7 @@ class TapRemoteMismatchError < RuntimeError
     @expected_remote = expected_remote
     @actual_remote = actual_remote
 
-    super <<-EOS.undent
+    super <<~EOS
       Tap #{name} remote mismatch.
       #{expected_remote} != #{actual_remote}
     EOS
@@ -248,7 +248,7 @@ class TapAlreadyTappedError < RuntimeError
   def initialize(name)
     @name = name
 
-    super <<-EOS.undent
+    super <<~EOS
       Tap #{name} already tapped.
     EOS
   end
@@ -260,7 +260,7 @@ class TapAlreadyUnshallowError < RuntimeError
   def initialize(name)
     @name = name
 
-    super <<-EOS.undent
+    super <<~EOS
       Tap #{name} already a full clone.
     EOS
   end
@@ -279,7 +279,7 @@ end
 
 class OperationInProgressError < RuntimeError
   def initialize(name)
-    message = <<-EOS.undent
+    message = <<~EOS
       Operation already in progress for #{name}
       Another active Homebrew process is already using #{name}.
       Please wait for it to finish or terminate it to continue.
@@ -327,7 +327,7 @@ class FormulaConflictError < RuntimeError
     message = []
     message << "Cannot install #{formula.full_name} because conflicting formulae are installed."
     message.concat conflicts.map { |c| conflict_message(c) } << ""
-    message << <<-EOS.undent
+    message << <<~EOS
       Please `brew unlink #{conflicts.map(&:name) * " "}` before continuing.
 
       Unlinking removes a formula's symlinks from #{HOMEBREW_PREFIX}. You can
@@ -341,7 +341,7 @@ end
 
 class FormulaAmbiguousPythonError < RuntimeError
   def initialize(formula)
-    super <<-EOS.undent
+    super <<~EOS
       The version of python to use with the virtualenv in the `#{formula.full_name}` formula
       cannot be guessed automatically. If the simultaneous use of python and python3
       is intentional, please add `:using => "python"` or `:using => "python3"` to
@@ -398,18 +398,18 @@ class BuildError < RuntimeError
       if formula.tap.official?
         puts Formatter.error(Formatter.url(OS::ISSUES_URL), label: "READ THIS")
       elsif issues_url = formula.tap.issues_url
-        puts <<-EOS.undent
+        puts <<~EOS
           If reporting this issue please do so at (not Homebrew/brew or Homebrew/core):
           #{Formatter.url(issues_url)}
         EOS
       else
-        puts <<-EOS.undent
+        puts <<~EOS
           If reporting this issue please do so to (not Homebrew/brew or Homebrew/core):
           #{formula.tap}
         EOS
       end
     else
-      puts <<-EOS.undent
+      puts <<~EOS
         Do not report this issue to Homebrew/brew or Homebrew/core!
       EOS
     end
@@ -445,7 +445,7 @@ class BuildToolsError < RuntimeError
       package_text = "a binary package"
     end
 
-    super <<-EOS.undent
+    super <<~EOS
       The following #{formula_text}:
         #{formulae.join(", ")}
       cannot be installed as #{package_text} and must be built from source.
@@ -467,7 +467,7 @@ class BuildFlagsError < RuntimeError
       require_text = "requires"
     end
 
-    super <<-EOS.undent
+    super <<~EOS
       The following #{flag_text}:
         #{flags.join(", ")}
       #{require_text} building tools, but none are installed.
@@ -481,7 +481,7 @@ end
 # the compilers available on the user's system
 class CompilerSelectionError < RuntimeError
   def initialize(formula)
-    super <<-EOS.undent
+    super <<~EOS
       #{formula.full_name} cannot be built with any available compilers.
       #{DevelopmentTools.custom_installation_instructions}
     EOS
@@ -491,7 +491,7 @@ end
 # Raised in Resource.fetch
 class DownloadError < RuntimeError
   def initialize(resource, cause)
-    super <<-EOS.undent
+    super <<~EOS
       Failed to download resource #{resource.download_name.inspect}
       #{cause.message}
       EOS
@@ -530,7 +530,7 @@ class ChecksumMismatchError < RuntimeError
     @expected = expected
     @hash_type = expected.hash_type.to_s.upcase
 
-    super <<-EOS.undent
+    super <<~EOS
       #{@hash_type} mismatch
       Expected: #{expected}
       Actual: #{actual}
@@ -557,7 +557,7 @@ class MissingApplyError < RuntimeError; end
 
 class BottleFormulaUnavailableError < RuntimeError
   def initialize(bottle_path, formula_path)
-    super <<-EOS.undent
+    super <<~EOS
       This bottle does not contain the formula file:
         #{bottle_path}
         #{formula_path}

Library/Homebrew/extend/ARGV.rb

@@ -124,7 +124,7 @@ module HomebrewArgvExtension
           Keg.new(prefix)
         end
       rescue FormulaUnavailableError
-        raise <<-EOS.undent
+        raise <<~EOS
           Multiple kegs installed to #{rack}
           However we don't know which one you refer to.
           Please delete (with rm -rf!) all but one and then try again.

Library/Homebrew/extend/ENV/shared.rb

@@ -233,7 +233,7 @@ module SharedEnvExtension
       if ARGV.include? "--default-fortran-flags"
         flags = FC_FLAG_VARS.reject { |key| self[key] }
       elsif values_at(*FC_FLAG_VARS).compact.empty?
-        opoo <<-EOS.undent
+        opoo <<~EOS
           No Fortran optimization information was provided.  You may want to consider
           setting FCFLAGS and FFLAGS or pass the `--default-fortran-flags` option to
           `brew install` if your compiler is compatible with GCC.
@@ -286,15 +286,15 @@ module SharedEnvExtension
     begin
       gcc_formula = gcc_version_formula(name)
     rescue FormulaUnavailableError => e
-      raise <<-EOS.undent
+      raise <<~EOS
-      Homebrew GCC requested, but formula #{e.name} not found!
+        Homebrew GCC requested, but formula #{e.name} not found!
       EOS
     end
 
     return if gcc_formula.opt_prefix.exist?
-    raise <<-EOS.undent
+    raise <<~EOS
-    The requested Homebrew GCC was not installed. You must:
+      The requested Homebrew GCC was not installed. You must:
-      brew install #{gcc_formula.full_name}
+        brew install #{gcc_formula.full_name}
     EOS
   end
 

Library/Homebrew/extend/git_repository.rb

@@ -36,6 +36,15 @@ module GitRepositoryExtension
     end
   end
 
+  def git_branch
+    return unless git? && Utils.git_available?
+    cd do
+      Utils.popen_read(
+        "git", "rev-parse", "--abbrev-ref", "HEAD"
+      ).chuzzle
+    end
+  end
+
   def git_last_commit_date
     return unless git? && Utils.git_available?
     cd do

Library/Homebrew/extend/os/caveats.rb

@@ -0,0 +1 @@
+require "extend/os/mac/caveats" if OS.mac?

Library/Homebrew/extend/os/linux/requirements/osxfuse_requirement.rb

@@ -18,7 +18,7 @@ class OsxfuseRequirement < Requirement
   def message
     msg = "libfuse is required to install this formula.\n"
     if libfuse_formula_exists?
-      msg + <<-EOS.undent
+      msg + <<~EOS
         Run "brew install libfuse" to install it.
       EOS
     else

Library/Homebrew/extend/os/mac/caveats.rb

@@ -0,0 +1,45 @@
+class Caveats
+  def plist_caveats
+    s = []
+    if f.plist || (keg&.plist_installed?)
+      plist_domain = f.plist_path.basename(".plist")
+
+      # we readlink because this path probably doesn't exist since caveats
+      # occurs before the link step of installation
+      # Yosemite security measures mildly tighter rules:
+      # https://github.com/Homebrew/legacy-homebrew/issues/33815
+      if !plist_path.file? || !plist_path.symlink?
+        if f.plist_startup
+          s << "To have launchd start #{f.full_name} now and restart at startup:"
+          s << "  sudo brew services start #{f.full_name}"
+        else
+          s << "To have launchd start #{f.full_name} now and restart at login:"
+          s << "  brew services start #{f.full_name}"
+        end
+      # For startup plists, we cannot tell whether it's running on launchd,
+      # as it requires for `sudo launchctl list` to get real result.
+      elsif f.plist_startup
+        s << "To restart #{f.full_name} after an upgrade:"
+        s << "  sudo brew services restart #{f.full_name}"
+      elsif Kernel.system "/bin/launchctl list #{plist_domain} &>/dev/null"
+        s << "To restart #{f.full_name} after an upgrade:"
+        s << "  brew services restart #{f.full_name}"
+      else
+        s << "To start #{f.full_name}:"
+        s << "  brew services start #{f.full_name}"
+      end
+
+      if f.plist_manual
+        s << "Or, if you don't want/need a background service you can just run:"
+        s << "  #{f.plist_manual}"
+      end
+
+      # pbpaste is the system clipboard tool on macOS and fails with `tmux` by default
+      # check if this is being run under `tmux` to avoid failing
+      if ENV["TMUX"] && !quiet_system("/usr/bin/pbpaste")
+        s << "" << "WARNING: brew services will fail when run under tmux."
+      end
+    end
+    s.join("\n") + "\n" unless s.empty?
+  end
+end

Library/Homebrew/extend/os/mac/development_tools.rb

@@ -24,18 +24,18 @@ class DevelopmentTools
 
     def installation_instructions
       if MacOS.version >= "10.9"
-        <<-EOS.undent
+        <<~EOS
           Install the Command Line Tools:
             xcode-select --install
         EOS
       elsif MacOS.version == "10.8" || MacOS.version == "10.7"
-        <<-EOS.undent
+        <<~EOS
           Install the Command Line Tools from
             https://developer.apple.com/download/more/
           or via Xcode's preferences.
         EOS
       else
-        <<-EOS.undent
+        <<~EOS
           Install Xcode from
             https://developer.apple.com/download/more/
         EOS
@@ -44,19 +44,19 @@ class DevelopmentTools
 
     def custom_installation_instructions
       if MacOS.version > :leopard
-        <<-EOS.undent
+        <<~EOS
           Install GNU's GCC
             brew install gcc
         EOS
       elsif MacOS.version > :tiger
-        <<-EOS.undent
+        <<~EOS
           Install GNU's GCC
             brew install gcc@4.6
         EOS
       else
         # Tiger doesn't ship with apple-gcc42, and this is required to build
         # some software that doesn't build properly with FSF GCC.
-        <<-EOS.undent
+        <<~EOS
           Install Apple's GCC
             brew install apple-gcc42
           or GNU's GCC

Library/Homebrew/extend/os/mac/diagnostic.rb

@@ -41,7 +41,7 @@ module Homebrew
           return
         end
 
-        <<-EOS.undent
+        <<~EOS
           You are using macOS #{MacOS.version}.
           #{who} do not provide support for this #{what}.
           You may encounter build failures or other breakages.
@@ -59,7 +59,7 @@ module Homebrew
         # Homebrew/brew is currently using.
         return if ENV["TRAVIS"]
 
-        message = <<-EOS.undent
+        message = <<~EOS
           Your Xcode (#{MacOS::Xcode.version}) is outdated.
           Please update to Xcode #{MacOS::Xcode.latest_version} (or delete it).
           #{MacOS::Xcode.update_instructions}
@@ -67,7 +67,7 @@ module Homebrew
 
         if OS::Mac.prerelease?
           current_path = Utils.popen_read("/usr/bin/xcode-select", "-p")
-          message += <<-EOS.undent
+          message += <<~EOS
             If #{MacOS::Xcode.latest_version} is installed, you may need to:
               sudo xcode-select --switch /Applications/Xcode.app
             Current developer directory is:
@@ -87,7 +87,7 @@ module Homebrew
         # Homebrew/brew is currently using.
         return if ENV["TRAVIS"]
 
-        <<-EOS.undent
+        <<~EOS
           A newer Command Line Tools release is available.
           #{MacOS::CLT.update_instructions}
         EOS
@@ -99,7 +99,7 @@ module Homebrew
         return unless MacOS.version == :el_capitan
         return unless MacOS::Xcode.version >= "8"
 
-        <<-EOS.undent
+        <<~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:
@@ -111,7 +111,7 @@ module Homebrew
         return unless MacOS::Xcode.installed?
         return unless MacOS::Xcode.below_minimum_version?
 
-        <<-EOS.undent
+        <<~EOS
           Your Xcode (#{MacOS::Xcode.version}) is too outdated.
           Please update to Xcode #{MacOS::Xcode.latest_version} (or delete it).
           #{MacOS::Xcode.update_instructions}
@@ -122,7 +122,7 @@ module Homebrew
         return unless MacOS::CLT.installed?
         return unless MacOS::CLT.below_minimum_version?
 
-        <<-EOS.undent
+        <<~EOS
           Your Command Line Tools are too outdated.
           #{MacOS::CLT.update_instructions}
         EOS
@@ -140,7 +140,7 @@ module Homebrew
           "Please install Xcode #{MacOS::Xcode.latest_version}."
         end
 
-        <<-EOS.undent
+        <<~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.
@@ -154,7 +154,7 @@ module Homebrew
         uninstaller = Pathname.new("/Developer/Library/uninstall-developer-folder")
         return unless ((MacOS::Xcode.version || "0") >= "4.3") && uninstaller.exist?
 
-        <<-EOS.undent
+        <<~EOS
           You have leftover files from an older version of Xcode.
           You should delete them using:
             #{uninstaller}
@@ -170,7 +170,7 @@ module Homebrew
         return if libs.empty?
         return if libs.include? "/usr/lib/libxcselect.dylib"
 
-        <<-EOS.undent
+        <<~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.
@@ -183,7 +183,7 @@ module Homebrew
         ponk = MacOS.macports_or_fink
         return if ponk.empty?
 
-        <<-EOS.undent
+        <<~EOS
           You have MacPorts or Fink installed:
             #{ponk.join(", ")}
 
@@ -199,7 +199,7 @@ module Homebrew
         return if RUBY_VERSION == ruby_version
         return if ARGV.homebrew_developer? && OS::Mac.prerelease?
 
-        <<-EOS.undent
+        <<~EOS
           Ruby version #{RUBY_VERSION} is unsupported on #{MacOS.version}. Homebrew
           is developed and tested on Ruby #{ruby_version}, and may not work correctly
           on other Rubies. Patches are accepted as long as they don't cause breakage
@@ -212,7 +212,7 @@ module Homebrew
         return if prefix.nil?
         return unless prefix.to_s.include?(" ")
 
-        <<-EOS.undent
+        <<~EOS
           Xcode is installed to a directory with a space in the name.
           This will cause some formulae to fail to build.
         EOS
@@ -222,7 +222,7 @@ module Homebrew
         prefix = MacOS::Xcode.prefix
         return if prefix.nil? || prefix.exist?
 
-        <<-EOS.undent
+        <<~EOS
           The directory Xcode is reportedly installed to doesn't exist:
             #{prefix}
           You may need to `xcode-select` the proper path if you have moved Xcode.
@@ -236,7 +236,7 @@ module Homebrew
 
         path = MacOS::Xcode.bundle_path
         path = "/Developer" if path.nil? || !path.directory?
-        <<-EOS.undent
+        <<~EOS
           Your Xcode is configured with an invalid path.
           You should change it to the correct path:
             sudo xcode-select -switch #{path}
@@ -247,7 +247,7 @@ module Homebrew
         return unless MacOS.version <= "10.8"
         return if Formula["curl"].installed?
 
-        <<-EOS.undent
+        <<~EOS
           The system curl on 10.8 and below is often incapable of supporting
           modern secure connections & will fail on fetching formulae.
 
@@ -261,7 +261,7 @@ module Homebrew
         return unless MacOS.version >= :yosemite
         return if ENV["SSL_CERT_DIR"].nil?
 
-        <<-EOS.undent
+        <<~EOS
           SSL_CERT_DIR support was removed from Apple's curl.
           If fetching formulae fails you should:
             unset SSL_CERT_DIR
@@ -274,7 +274,7 @@ module Homebrew
         # license or no "xc*" tool will work.
         return unless `/usr/bin/xcrun clang 2>&1` =~ /license/ && !$CHILD_STATUS.success?
 
-        <<-EOS.undent
+        <<~EOS
           You have not agreed to the Xcode license.
           Builds will fail! Agree to the license by opening Xcode.app or running:
             sudo xcodebuild -license
@@ -289,7 +289,7 @@ module Homebrew
         latest_version = Version.create(MacOS::XQuartz.latest_version)
         return if installed_version >= latest_version
 
-        <<-EOS.undent
+        <<~EOS
           Your XQuartz (#{installed_version}) is outdated.
           Please install XQuartz #{latest_version} (or delete the current version).
           XQuartz can be updated using Homebrew-Cask by running
@@ -301,7 +301,7 @@ module Homebrew
         return unless MacOS::XQuartz.version
         return unless MacOS::XQuartz.version.include? "beta"
 
-        <<-EOS.undent
+        <<~EOS
           The following beta release of XQuartz is installed: #{MacOS::XQuartz.version}
 
           XQuartz beta releases include address sanitization, and do not work with
@@ -337,7 +337,7 @@ module Homebrew
         end
         case_sensitive_vols.uniq!
 
-        <<-EOS.undent
+        <<~EOS
           The filesystem on #{case_sensitive_vols.join(",")} appears to be case-sensitive.
           The default macOS filesystem is case-insensitive. Please report any apparent problems.
         EOS
@@ -346,7 +346,7 @@ module Homebrew
       def check_homebrew_prefix
         return if HOMEBREW_PREFIX.to_s == "/usr/local"
 
-        <<-EOS.undent
+        <<~EOS
           Your Homebrew's prefix is not /usr/local.
           You can install Homebrew anywhere you want but some bottles (binary packages)
           can only be used with a /usr/local prefix and some formulae (packages)
@@ -360,7 +360,7 @@ module Homebrew
 
         mono_config = Pathname.new("/usr/bin/pkg-config")
         if mono_config.exist? && mono_config.realpath.to_s.include?("Mono.framework")
-          <<-EOS.undent
+          <<~EOS
             You have a non-Homebrew 'pkg-config' in your PATH:
               /usr/bin/pkg-config => #{mono_config.realpath}
 
@@ -371,7 +371,7 @@ module Homebrew
             `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.undent
+          <<~EOS
             You have a non-Homebrew 'pkg-config' in your PATH:
               #{binary}
 

Library/Homebrew/extend/os/mac/formula_cellar_checks.rb

@@ -19,7 +19,7 @@ module FormulaCellarChecks
 
     return if files.empty?
 
-    <<-EOS.undent
+    <<~EOS
       Header files that shadow system header files were installed to "#{formula.include}"
       The offending files are:
         #{files * "\n        "}
@@ -35,7 +35,7 @@ module FormulaCellarChecks
     end
     return if system_openssl.empty?
 
-    <<-EOS.undent
+    <<~EOS
       object files were linked against system openssl
       These object files were linked against the deprecated system OpenSSL or
       the system's private LibreSSL.
@@ -52,7 +52,7 @@ module FormulaCellarChecks
     end
     return if framework_links.empty?
 
-    <<-EOS.undent
+    <<~EOS
       python modules have explicit framework links
       These python extension modules were linked directly to a Python
       framework binary. They should be linked with -undefined dynamic_lookup
@@ -67,13 +67,13 @@ module FormulaCellarChecks
     checker = LinkageChecker.new(keg, formula)
 
     return unless checker.broken_dylibs?
-    output = <<-EOS.undent
+    output = <<~EOS
       #{formula} has broken dynamic library links:
         #{checker.broken_dylibs.to_a * "\n  "}
     EOS
     tab = Tab.for_keg(keg)
     if tab.poured_from_bottle
-      output += <<-EOS.undent
+      output += <<~EOS
         Rebuild this from source with:
           brew reinstall --build-from-source #{formula}
         If that's successful, file an issue#{formula.tap ? " here:\n  #{formula.tap.issues_url}" : "."}

Library/Homebrew/extend/os/mac/missing_formula.rb

@@ -5,12 +5,12 @@ module Homebrew
         case name.downcase
         when "xcode"
           if MacOS.version >= :lion
-            <<-EOS.undent
+            <<~EOS
-            Xcode can be installed from the App Store.
+              Xcode can be installed from the App Store.
             EOS
           else
-            <<-EOS.undent
+            <<~EOS
-            Xcode can be installed from #{Formatter.url("https://developer.apple.com/download/more/")}.
+              Xcode can be installed from #{Formatter.url("https://developer.apple.com/download/more/")}.
             EOS
           end
         else

Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb

@@ -26,7 +26,7 @@ class NonBinaryOsxfuseRequirement < Requirement
   satisfy(build_env: false) { HOMEBREW_PREFIX.to_s != "/usr/local" || !OsxfuseRequirement.binary_osxfuse_installed? }
 
   def message
-    <<-EOS.undent
+    <<~EOS
       osxfuse is already installed from the binary distribution and
       conflicts with this formula.
     EOS

Library/Homebrew/extend/pathname.rb

@@ -403,7 +403,7 @@ class Pathname
     mkpath
     targets.each do |target|
       target = Pathname.new(target) # allow pathnames or strings
-      join(target.basename).write <<-EOS.undent
+      join(target.basename).write <<~EOS
         #!/bin/bash
         exec "#{target}" "$@"
       EOS
@@ -415,9 +415,9 @@ class Pathname
     env_export = ""
     env.each { |key, value| env_export += "#{key}=\"#{value}\" " }
     dirname.mkpath
-    write <<-EOS.undent
+    write <<~EOS
-    #!/bin/bash
+      #!/bin/bash
-    #{env_export}exec "#{target}" "$@"
+      #{env_export}exec "#{target}" "$@"
     EOS
   end
 
@@ -435,7 +435,7 @@ class Pathname
   # Writes an exec script that invokes a java jar
   def write_jar_script(target_jar, script_name, java_opts = "")
     mkpath
-    join(script_name).write <<-EOS.undent
+    join(script_name).write <<~EOS
       #!/bin/bash
       exec java #{java_opts} -jar #{target_jar} "$@"
     EOS

Library/Homebrew/extend/string.rb

@@ -2,23 +2,6 @@
 require_relative "../vendor/backports/string"
 
 class String
-  def undent
-    gsub(/^[ \t]{#{(slice(/^[ \t]+/) || '').length}}/, "")
-  end
-  alias unindent undent
-
-  # eg:
-  #   if foo then <<-EOS.undent_________________________________________________________72
-  #               Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do
-  #               eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
-  #               minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip
-  #               ex ea commodo consequat. Duis aute irure dolor in reprehenderit in
-  #               voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur
-  #               sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt
-  #               mollit anim id est laborum.
-  #               EOS
-  alias undent_________________________________________________________72 undent
-
   # String.chomp, but if result is empty: returns nil instead.
   # Allows `chuzzle || foo` short-circuits.
   def chuzzle

Library/Homebrew/formula.rb

@@ -839,7 +839,7 @@ class Formula
   # This method can be overridden to provide a plist.
   # For more examples read Apple's handy manpage:
   # https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man5/plist.5.html
-  # <pre>def plist; <<-EOS.undent
+  # <pre>def plist; <<~EOS
   #  <?xml version="1.0" encoding="UTF-8"?>
   #  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   #  <plist version="1.0">
@@ -986,13 +986,13 @@ class Formula
   # to installation through a different package manager on a different OS.
   # @return [String]
   # <pre>def caveats
-  #   <<-EOS.undent
+  #   <<~EOS
   #     Are optional. Something the user should know?
   #   EOS
   # end</pre>
   #
   # <pre>def caveats
-  #   s = <<-EOS.undent
+  #   s = <<~EOS
   #     Print some important notice to the user when `brew info <formula>` is
   #     called or when brewing a formula.
   #     This is optional. You can use all the vars like #{version} here.
@@ -1691,7 +1691,7 @@ class Formula
     # keep Homebrew's site-packages in sys.path when using system Python
     user_site_packages = home/"Library/Python/2.7/lib/python/site-packages"
     user_site_packages.mkpath
-    (user_site_packages/"homebrew.pth").write <<-EOS.undent
+    (user_site_packages/"homebrew.pth").write <<~EOS
       import site; site.addsitedir("#{HOMEBREW_PREFIX}/lib/python2.7/site-packages")
       import sys, os; sys.path = (os.environ["PYTHONPATH"].split(os.pathsep) if "PYTHONPATH" in os.environ else []) + ["#{HOMEBREW_PREFIX}/lib/python2.7/site-packages"] + sys.path
     EOS
@@ -2394,7 +2394,7 @@ class Formula
     # and building the software was ok.
     # <pre>system bin/"foobar", "--version"</pre>
     #
-    # <pre>(testpath/"test.file").write <<-EOS.undent
+    # <pre>(testpath/"test.file").write <<~EOS
     #   writing some test file, if you need to
     # EOS
     # assert_equal "OK", shell_output("test_command test.file").strip</pre>

Library/Homebrew/formula_cellar_checks.rb

@@ -12,7 +12,7 @@ module FormulaCellarChecks
     prefix_bin = prefix_bin.realpath
     return if ORIGINAL_PATHS.include? prefix_bin
 
-    <<-EOS.undent
+    <<~EOS
       #{prefix_bin} is not in your PATH
       You can amend this by altering your #{Utils::Shell.profile} file
     EOS
@@ -22,7 +22,7 @@ module FormulaCellarChecks
     # Check for man pages that aren't in share/man
     return unless (formula.prefix/"man").directory?
 
-    <<-EOS.undent
+    <<~EOS
       A top-level "man" directory was found
       Homebrew requires that man pages live under share.
       This can often be fixed by passing "--mandir=\#{man}" to configure.
@@ -33,7 +33,7 @@ module FormulaCellarChecks
     # Check for info pages that aren't in share/info
     return unless (formula.prefix/"info").directory?
 
-    <<-EOS.undent
+    <<~EOS
       A top-level "info" directory was found
       Homebrew suggests that info pages live under share.
       This can often be fixed by passing "--infodir=\#{info}" to configure.
@@ -45,7 +45,7 @@ module FormulaCellarChecks
     jars = formula.lib.children.select { |g| g.extname == ".jar" }
     return if jars.empty?
 
-    <<-EOS.undent
+    <<~EOS
       JARs were installed to "#{formula.lib}"
       Installing JARs to "lib" can cause conflicts between packages.
       For Java software, it is typically better for the formula to
@@ -67,7 +67,7 @@ module FormulaCellarChecks
     end
     return if non_libraries.empty?
 
-    <<-EOS.undent
+    <<~EOS
       Non-libraries were installed to "#{formula.lib}"
       Installing non-libraries to "lib" is discouraged.
       The offending files are:
@@ -81,7 +81,7 @@ module FormulaCellarChecks
     non_exes = bin.children.select { |g| g.directory? || !g.executable? }
     return if non_exes.empty?
 
-    <<-EOS.undent
+    <<~EOS
       Non-executables were installed to "#{bin}"
       The offending files are:
         #{non_exes * "\n        "}
@@ -94,7 +94,7 @@ module FormulaCellarChecks
     generics = bin.children.select { |g| generic_names.include? g.basename.to_s }
     return if generics.empty?
 
-    <<-EOS.undent
+    <<~EOS
       Generic binaries were installed to "#{bin}"
       Binaries with generic names are likely to conflict with other software,
       and suggest that this software should be installed to "libexec" and then
@@ -109,7 +109,7 @@ module FormulaCellarChecks
     pth_found = Dir["#{lib}/python{2.7,3}*/site-packages/easy-install.pth"].map { |f| File.dirname(f) }
     return if pth_found.empty?
 
-    <<-EOS.undent
+    <<~EOS
       easy-install.pth files were found
       These .pth files are likely to cause link conflicts. Please invoke
       setup.py using Language::Python.setup_install_args.
@@ -128,7 +128,7 @@ module FormulaCellarChecks
     end
 
     return unless bad_dir_name
-    <<-EOS
+    <<~EOS
       Emacs Lisp files were installed into the wrong site-lisp subdirectory.
       They should be installed into:
       #{share}/emacs/site-lisp/#{name}
@@ -142,7 +142,7 @@ module FormulaCellarChecks
 
     elisps = (share/"emacs/site-lisp").children.select { |file| %w[.el .elc].include? file.extname }
     return if elisps.empty?
-    <<-EOS.undent
+    <<~EOS
       Emacs Lisp files were linked directly to #{HOMEBREW_PREFIX}/share/emacs/site-lisp
       This may cause conflicts with other packages.
       They should instead be installed into:

Library/Homebrew/formula_installer.rb

@@ -93,7 +93,7 @@ class FormulaInstaller
     return false if formula.bottle_disabled?
     unless formula.pour_bottle?
       if install_bottle_options[:warn] && formula.pour_bottle_check_unsatisfied_reason
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Building #{formula.full_name} from source:
             #{formula.pour_bottle_check_unsatisfied_reason}
         EOS
@@ -104,7 +104,7 @@ class FormulaInstaller
     bottle = formula.bottle_specification
     unless bottle.compatible_cellar?
       if install_bottle_options[:warn]
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Building #{formula.full_name} from source:
             The bottle needs a #{bottle.cellar} Cellar (yours is #{HOMEBREW_CELLAR}).
         EOS
@@ -165,14 +165,14 @@ class FormulaInstaller
     end
 
     unless recursive_dependencies.empty?
-      raise CannotInstallFormulaError, <<-EOS.undent
+      raise CannotInstallFormulaError, <<~EOS
         #{formula.full_name} contains a recursive dependency on itself:
           #{recursive_dependencies.join("\n  ")}
       EOS
     end
 
     if recursive_formulae.flat_map(&:recursive_dependencies).map(&:to_s).include?(formula.name)
-      raise CannotInstallFormulaError, <<-EOS.undent
+      raise CannotInstallFormulaError, <<~EOS
         #{formula.full_name} contains a recursive dependency on itself!
       EOS
     end
@@ -188,7 +188,7 @@ class FormulaInstaller
       version_conflicts += version_hash[unversioned_name]
     end
     unless version_conflicts.empty?
-      raise CannotInstallFormulaError, <<-EOS.undent
+      raise CannotInstallFormulaError, <<~EOS
         #{formula.full_name} contains conflicting version recursive dependencies:
           #{version_conflicts.to_a.join ", "}
         View these with `brew deps --tree #{formula.full_name}`.
@@ -221,16 +221,16 @@ class FormulaInstaller
     # function but after instantiating this class so that it can avoid having to
     # relink the active keg if possible (because it is slow).
     if formula.linked_keg.directory?
-      message = <<-EOS.undent
+      message = <<~EOS
         #{formula.name} #{formula.linked_version} is already installed
       EOS
       message += if formula.outdated? && !formula.head?
-        <<-EOS.undent
+        <<~EOS
           To upgrade to #{formula.pkg_version}, run `brew upgrade #{formula.name}`
         EOS
       else
         # some other version is already installed *and* linked
-        <<-EOS.undent
+        <<~EOS
           To install #{formula.pkg_version}, first run `brew unlink #{formula.name}`
         EOS
       end
@@ -355,7 +355,7 @@ class FormulaInstaller
       rescue FormulaUnavailableError => e
         # If the formula name doesn't exist any more then complain but don't
         # stop installation from continuing.
-        opoo <<-EOS.undent
+        opoo <<~EOS
           #{formula}: #{e.message}
           'conflicts_with \"#{c.name}\"' should be removed from #{formula.path.basename}.
         EOS

Library/Homebrew/formula_support.rb

@@ -33,33 +33,33 @@ class KegOnlyReason
   def to_s
     return @explanation unless @explanation.empty?
     case @reason
-    when :versioned_formula then <<-EOS.undent
+    when :versioned_formula then <<~EOS
       this is an alternate version of another formula
     EOS
-    when :provided_by_macos, :provided_by_osx then <<-EOS.undent
+    when :provided_by_macos, :provided_by_osx then <<~EOS
       macOS already provides this software and installing another version in
       parallel can cause all kinds of trouble
     EOS
-    when :shadowed_by_macos, :shadowed_by_osx then <<-EOS.undent
+    when :shadowed_by_macos, :shadowed_by_osx 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.undent
+    when :provided_pre_mountain_lion then <<~EOS
       macOS already provides this software in versions before Mountain Lion
     EOS
-    when :provided_pre_mavericks then <<-EOS.undent
+    when :provided_pre_mavericks then <<~EOS
       macOS already provides this software in versions before Mavericks
     EOS
-    when :provided_pre_el_capitan then <<-EOS.undent
+    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.undent
+    when :provided_pre_high_sierra then <<~EOS
       macOS already provides this software in versions before High Sierra
     EOS
-    when :provided_until_xcode43 then <<-EOS.undent
+    when :provided_until_xcode43 then <<~EOS
       Xcode provides this software prior to version 4.3
     EOS
-    when :provided_until_xcode5 then <<-EOS.undent
+    when :provided_until_xcode5 then <<~EOS
       Xcode provides this software prior to version 5
     EOS
     else

Library/Homebrew/formulary.rb

@@ -128,7 +128,7 @@ module Formulary
       formula = begin
         Formulary.from_contents name, @bottle_filename, contents, spec
       rescue FormulaUnreadableError => e
-        opoo <<-EOS.undent
+        opoo <<~EOS
           Unreadable formula in #{@bottle_filename}:
           #{e}
         EOS
@@ -443,7 +443,7 @@ module Formulary
     if possible_pinned_tap_formulae.size == 1
       selected_formula = factory(possible_pinned_tap_formulae.first, spec)
       if core_path(ref).file?
-        opoo <<-EOS.undent
+        opoo <<~EOS
           #{ref} is provided by core, but is now shadowed by #{selected_formula.full_name}.
           To refer to the core formula, use Homebrew/core/#{ref} instead.
         EOS

Library/Homebrew/gpg.rb

@@ -32,7 +32,7 @@ class Gpg
   def self.create_test_key(path)
     odie "No GPG present to test against!" unless available?
 
-    (path/"batch.gpg").write <<-EOS.undent
+    (path/"batch.gpg").write <<~EOS
       Key-Type: RSA
       Key-Length: 2048
       Subkey-Type: RSA

Library/Homebrew/keg.rb

@@ -6,7 +6,7 @@ require "ostruct"
 class Keg
   class AlreadyLinkedError < RuntimeError
     def initialize(keg)
-      super <<-EOS.undent
+      super <<~EOS
         Cannot link #{keg.name}
         Another version is already linked: #{keg.linked_keg_record.resolved_path}
         EOS
@@ -32,9 +32,9 @@ class Keg
     rescue NotAKegError, Errno::ENOENT
       "already exists. You may want to remove it:\n  rm '#{dst}'\n"
     else
-      <<-EOS.undent
+      <<~EOS
-      is a symlink belonging to #{conflict.name}. You can unlink it:
+        is a symlink belonging to #{conflict.name}. You can unlink it:
-        brew unlink #{conflict.name}
+          brew unlink #{conflict.name}
       EOS
     end
 
@@ -42,7 +42,7 @@ class Keg
       s = []
       s << "Could not symlink #{src}"
       s << "Target #{dst}" << suggestion
-      s << <<-EOS.undent
+      s << <<~EOS
         To force the link and overwrite all conflicting files:
           brew link --overwrite #{keg.name}
 
@@ -54,7 +54,7 @@ class Keg
   end
 
   class DirectoryNotWritableError < LinkError
-    def to_s; <<-EOS.undent
+    def to_s; <<~EOS
       Could not symlink #{src}
       #{dst.dirname} is not writable.
       EOS

Library/Homebrew/language/python.rb

@@ -46,7 +46,7 @@ module Language
     end
 
     def self.in_sys_path?(python, path)
-      script = <<-EOS.undent
+      script = <<~EOS
         import os, sys
         [os.path.realpath(p) for p in sys.path].index(os.path.realpath("#{path}"))
       EOS
@@ -54,7 +54,7 @@ module Language
     end
 
     def self.setup_install_args(prefix)
-      shim = <<-EOS.undent
+      shim = <<~EOS
         import setuptools, tokenize
         __file__ = 'setup.py'
         exec(compile(getattr(tokenize, 'open', open)(__file__).read()

Library/Homebrew/migrator.rb

@@ -6,7 +6,7 @@ require "tab"
 class Migrator
   class MigrationNeededError < RuntimeError
     def initialize(formula)
-      super <<-EOS.undent
+      super <<~EOS
         #{formula.oldname} was renamed to #{formula.name} and needs to be migrated.
         Please run `brew migrate #{formula.oldname}`
       EOS
@@ -33,10 +33,9 @@ class Migrator
         "Please try to use fully-qualified #{tap}/#{formula.oldname} to refer the formula.\n"
       end
 
-      super <<-EOS.undent
+      super <<~EOS
-      #{formula.name} from #{formula.tap} is given, but old name #{formula.oldname} was installed from #{tap ? tap : "path or url"}.
+        #{formula.name} from #{formula.tap} is given, but old name #{formula.oldname} was installed from #{tap ? tap : "path or url"}.
-
+         #{msg}To force migrate use `brew migrate --force #{formula.oldname}`.
-      #{msg}To force migrate use `brew migrate --force #{formula.oldname}`.
       EOS
     end
   end

Library/Homebrew/missing_formula.rb

@@ -12,10 +12,10 @@ module Homebrew
 
       def blacklisted_reason(name)
         case name.downcase
-        when "gem", /^rubygems?$/ then <<-EOS.undent
+        when "gem", /^rubygems?$/ then <<~EOS
           Homebrew provides gem via: `brew install ruby`.
           EOS
-        when "tex", "tex-live", "texlive", "latex" then <<-EOS.undent
+        when "tex", "tex-live", "texlive", "latex" then <<~EOS
           Installing TeX from source is weird and gross, requires a lot of patches,
           and only builds 32-bit (and thus can't use Homebrew dependencies)
 
@@ -24,42 +24,42 @@ module Homebrew
           You can install it with Homebrew-Cask:
             brew cask install mactex
           EOS
-        when "pip" then <<-EOS.undent
+        when "pip" then <<~EOS
           Homebrew provides pip via: `brew install python`. However you will then
           have two Pythons installed on your Mac, so alternatively you can install
           pip via the instructions at:
             #{Formatter.url("https://pip.readthedocs.io/en/stable/installing/")}
           EOS
-        when "pil" then <<-EOS.undent
+        when "pil" then <<~EOS
           Instead of PIL, consider `pip2 install pillow`.
           EOS
-        when "macruby" then <<-EOS.undent
+        when "macruby" then <<~EOS
           MacRuby is not packaged and is on an indefinite development hiatus.
           You can read more about it at:
             #{Formatter.url("https://github.com/MacRuby/MacRuby")}
           EOS
         when /(lib)?lzma/
           "lzma is now part of the xz formula."
-        when "gtest", "googletest", "google-test" then <<-EOS.undent
+        when "gtest", "googletest", "google-test" then <<~EOS
           Installing gtest system-wide is not recommended; it should be vendored
           in your projects that use it.
           EOS
-        when "gmock", "googlemock", "google-mock" then <<-EOS.undent
+        when "gmock", "googlemock", "google-mock" then <<~EOS
           Installing gmock system-wide is not recommended; it should be vendored
           in your projects that use it.
           EOS
-        when "sshpass" then <<-EOS.undent
+        when "sshpass" then <<~EOS
           We won't add sshpass because it makes it too easy for novice SSH users to
           ruin SSH's security.
           EOS
-        when "gsutil" then <<-EOS.undent
+        when "gsutil" then <<~EOS
           Install gsutil with `pip2 install gsutil`
           EOS
-        when "gfortran" then <<-EOS.undent
+        when "gfortran" then <<~EOS
           GNU Fortran is now provided as part of GCC, and can be installed with:
             brew install gcc
           EOS
-        when "play" then <<-EOS.undent
+        when "play" then <<~EOS
           Play 2.3 replaces the play command with activator:
             brew install typesafe-activator
 
@@ -67,7 +67,7 @@ module Homebrew
             #{Formatter.url("https://www.playframework.com/documentation/2.3.x/Migration23")}
             #{Formatter.url("https://www.playframework.com/documentation/2.3.x/Highlights23")}
           EOS
-        when "haskell-platform" then <<-EOS.undent
+        when "haskell-platform" then <<~EOS
           We no longer package haskell-platform. Consider installing ghc
           and cabal-install instead:
             brew install ghc cabal-install
@@ -75,10 +75,10 @@ module Homebrew
           You can install with Homebrew-Cask:
             brew cask install haskell-platform
           EOS
-        when "mysqldump-secure" then <<-EOS.undent
+        when "mysqldump-secure" then <<~EOS
           The creator of mysqldump-secure tried to game our popularity metrics.
           EOS
-        when "ngrok" then <<-EOS.undent
+        when "ngrok" then <<~EOS
           Upstream sunsetted 1.x in March 2016 and 2.x is not open-source.
 
           If you wish to use the 2.x release you can install with Homebrew-Cask:
@@ -98,12 +98,12 @@ module Homebrew
           new_tap_user, new_tap_repo, = new_tap.split("/")
           new_tap_name = "#{new_tap_user}/#{new_tap_repo}"
 
-          message = <<-EOS.undent
+          message = <<~EOS
             It was migrated from #{old_tap} to #{new_tap}.
           EOS
           break if new_tap_name == CoreTap.instance.name
 
-          message += <<-EOS.undent
+          message += <<~EOS
             You can access it again by running:
               brew tap #{new_tap_name}
           EOS
@@ -124,7 +124,7 @@ module Homebrew
           unless silent
             ohai "Searching for a previously deleted formula..."
             if (tap.path/".git/shallow").exist?
-              opoo <<-EOS.undent
+              opoo <<~EOS
                 #{tap} is shallow clone. To get complete history run:
                   git -C "$(brew --repo #{tap})" fetch --unshallow
 
@@ -147,7 +147,7 @@ module Homebrew
           commit_message.sub!(/ \(#(\d+)\)$/, " (#{tap.issues_url}/\\1)")
           commit_message.gsub!(/(Closes|Fixes) #(\d+)/, "\\1 #{tap.issues_url}/\\2")
 
-          <<-EOS.undent
+          <<~EOS
             #{name} was deleted from #{tap.name} in commit #{short_hash}:
               #{commit_message}
 

Library/Homebrew/os/mac.rb

@@ -201,6 +201,7 @@ module OS
       "8.3.2" => { clang: "8.1", clang_build: 802 },
       "8.3.3" => { clang: "8.1", clang_build: 802 },
       "9.0"   => { clang: "9.0", clang_build: 900 },
+      "9.0.1" => { clang: "9.0", clang_build: 900 },
     }.freeze
 
     def compilers_standard?
@@ -208,7 +209,7 @@ module OS
         send(:"#{method}_version") == build
       end
     rescue IndexError
-      onoe <<-EOS.undent
+      onoe <<~EOS
         Homebrew doesn't know what compiler versions ship with your version
         of Xcode (#{Xcode.version}). Please `brew update` and if that doesn't
         help, file an issue with the output of `brew --config`:

Library/Homebrew/os/mac/keg.rb

@@ -5,7 +5,7 @@ class Keg
     puts "Changing dylib ID of #{file}\n  from #{file.dylib_id}\n    to #{id}" if ARGV.debug?
     MachO::Tools.change_dylib_id(file, id, strict: false)
   rescue MachO::MachOError
-    onoe <<-EOS.undent
+    onoe <<~EOS
       Failed changing dylib ID of #{file}
         from #{file.dylib_id}
           to #{id}
@@ -19,7 +19,7 @@ class Keg
     puts "Changing install name in #{file}\n  from #{old}\n    to #{new}" if ARGV.debug?
     MachO::Tools.change_install_name(file, old, new, strict: false)
   rescue MachO::MachOError
-    onoe <<-EOS.undent
+    onoe <<~EOS
       Failed changing install name in #{file}
         from #{old}
           to #{new}

Library/Homebrew/os/mac/xcode.rb

@@ -17,13 +17,13 @@ module OS
         when "10.9"  then "6.2"
         when "10.10" then "7.2.1"
         when "10.11" then "8.2.1"
-        when "10.12" then "8.3.3"
+        when "10.12" then "9.0.1"
-        when "10.13" then "9.0"
+        when "10.13" then "9.0.1"
         else
           raise "macOS '#{MacOS.version}' is invalid" unless OS::Mac.prerelease?
 
           # Default to newest known version of Xcode for unreleased macOS versions.
-          "9.0"
+          "9.0.1"
         end
       end
 
@@ -86,11 +86,11 @@ module OS
 
       def update_instructions
         if MacOS.version >= "10.9" && !OS::Mac.prerelease?
-          <<-EOS.undent
+          <<~EOS
             Xcode can be updated from the App Store.
           EOS
         else
-          <<-EOS.undent
+          <<~EOS
             Xcode can be updated from
               https://developer.apple.com/download/more/
           EOS
@@ -199,11 +199,11 @@ module OS
 
       def update_instructions
         if MacOS.version >= "10.9"
-          <<-EOS.undent
+          <<~EOS
             Update them from Software Update in the App Store.
           EOS
         elsif MacOS.version == "10.8" || MacOS.version == "10.7"
-          <<-EOS.undent
+          <<~EOS
             The standalone package can be obtained from
               https://developer.apple.com/download/more/
             or it can be installed via Xcode's preferences.
@@ -216,8 +216,8 @@ 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 "900.0.37"
+        when "10.13" then "900.0.38"
-        when "10.12" then "802.0.42"
+        when "10.12" then "900.0.38"
         when "10.11" then "800.0.42.1"
         when "10.10" then "700.1.81"
         when "10.9"  then "600.0.57"

Library/Homebrew/patch.rb

@@ -139,7 +139,7 @@ class ExternalPatch
       if patch_files.empty?
         children = patch_dir.children
         if children.length != 1 || !children.first.file?
-          raise MissingApplyError, <<-EOS.undent
+          raise MissingApplyError, <<~EOS
             There should be exactly one patch file in the staging directory unless
             the "apply" method was used one or more times in the patch-do block.
           EOS

Library/Homebrew/requirement.rb

@@ -35,18 +35,16 @@ class Requirement
     _, _, class_name = self.class.to_s.rpartition "::"
     s = "#{class_name} unsatisfied!\n"
     if cask
-      s += <<-EOS.undent
+      s += <<~EOS
-
         You can install with Homebrew-Cask:
-          brew cask install #{cask}
+         brew cask install #{cask}
       EOS
     end
 
     if download
-      s += <<-EOS.undent
+      s += <<~EOS
-
         You can download from:
-          #{download}
+         #{download}
       EOS
     end
     s

Library/Homebrew/requirements.rb

@@ -2,7 +2,8 @@ require "requirement"
 require "requirements/fortran_requirement"
 require "requirements/gpg2_requirement"
 require "requirements/language_module_requirement"
-require "requirements/minimum_macos_requirement"
+require "requirements/linux_requirement"
+require "requirements/macos_requirement"
 require "requirements/maximum_macos_requirement"
 require "requirements/mpi_requirement"
 require "requirements/osxfuse_requirement"
@@ -33,16 +34,16 @@ class XcodeRequirement < Requirement
 
   def message
     version = " #{@version}" if @version
-    message = <<-EOS.undent
+    message = <<~EOS
       A full installation of Xcode.app#{version} is required to compile this software.
       Installing just the Command Line Tools is not sufficient.
     EOS
     if MacOS.version >= :lion
-      message + <<-EOS.undent
+      message + <<~EOS
         Xcode can be installed from the App Store.
       EOS
     else
-      message + <<-EOS.undent
+      message + <<~EOS
         Xcode can be installed from #{Formatter.url("https://developer.apple.com/download/more/")}.
       EOS
     end
@@ -82,7 +83,7 @@ class TeXRequirement < Requirement
   satisfy { which("tex") || which("latex") }
 
   def message
-    s = <<-EOS.undent
+    s = <<~EOS
       A LaTeX distribution is required for Homebrew to install this formula.
 
       Make sure that "/usr/texbin", or the location you installed it to, is in

Library/Homebrew/requirements/java_requirement.rb

@@ -11,7 +11,7 @@ class JavaRequirement < Requirement
   end
 
   def initialize(tags)
-    @version = tags.shift if /(\d\.)+\d/ =~ tags.first
+    @version = tags.shift if /(\d+\.)+\d/ =~ tags.first
     super
   end
 
@@ -103,7 +103,7 @@ class JavaRequirement < Requirement
   end
 
   def satisfies_version(java)
-    java_version_s = Utils.popen_read("#{java} -version 2>&1")[/1.\d/]
+    java_version_s = Utils.popen_read("#{java} -version 2>&1")[/\d+.\d/]
     return false unless java_version_s
     java_version = Version.create(java_version_s)
     needed_version = Version.create(version_without_plus)

Library/Homebrew/requirements/language_module_requirement.rb

@@ -13,16 +13,15 @@ class LanguageModuleRequirement < Requirement
   satisfy(build_env: false) { quiet_system(*the_test) }
 
   def message
-    s = <<-EOS.undent
+    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.undent
+      s += <<~EOS
-
+        You may need to: `brew install #{@language}`
-      You may need to: `brew install #{@language}`
 
       EOS
     end

Library/Homebrew/requirements/linux_requirement.rb

@@ -0,0 +1,9 @@
+class LinuxRequirement < Requirement
+  fatal true
+
+  satisfy(build_env: false) { OS.linux? }
+
+  def message
+    "Linux is required."
+  end
+end

Library/Homebrew/requirements/macos_requirement.rb

@@ -0,0 +1,31 @@
+require "requirement"
+
+class MacOSRequirement < Requirement
+  fatal true
+
+  def initialize(tags = [])
+    @version = MacOS::Version.from_symbol(tags.first) unless tags.empty?
+    super
+  end
+
+  def minimum_version_specified?
+    OS.mac? && @version
+  end
+
+  satisfy(build_env: false) do
+    next MacOS.version >= @version if minimum_version_specified?
+    next true if OS.mac?
+    next true if @version
+    false
+  end
+
+  def message
+    return "macOS is required." unless minimum_version_specified?
+    "macOS #{@version.pretty_name} or newer is required."
+  end
+
+  def display_s
+    return "macOS is required" unless minimum_version_specified?
+    "macOS >= #{@version}"
+  end
+end

Library/Homebrew/requirements/maximum_macos_requirement.rb

@@ -11,7 +11,7 @@ class MaximumMacOSRequirement < Requirement
   satisfy(build_env: false) { MacOS.version <= @version }
 
   def message
-    <<-EOS.undent
+    <<~EOS
       This formula either does not compile or function as expected on macOS
       versions newer than #{@version.pretty_name} due to an upstream incompatibility.
     EOS

Library/Homebrew/requirements/minimum_macos_requirement.rb

@@ -1,20 +0,0 @@
-require "requirement"
-
-class MinimumMacOSRequirement < Requirement
-  fatal true
-
-  def initialize(tags)
-    @version = MacOS::Version.from_symbol(tags.first)
-    super
-  end
-
-  satisfy(build_env: false) { MacOS.version >= @version }
-
-  def message
-    "macOS #{@version.pretty_name} or newer is required."
-  end
-
-  def display_s
-    "macOS >= #{@version}"
-  end
-end

Library/Homebrew/requirements/unsigned_kext_requirement.rb

@@ -6,7 +6,7 @@ class UnsignedKextRequirement < Requirement
   satisfy(build_env: false) { MacOS.version < :yosemite }
 
   def message
-    s = <<-EOS.undent
+    s = <<~EOS
       Building this formula from source isn't possible due to OS X
       Yosemite (10.10) and above's strict unsigned kext ban.
     EOS

Library/Homebrew/rubocops/conflicts_cop.rb

@@ -6,7 +6,7 @@ module RuboCop
     module FormulaAudit
       # This cop audits versioned Formulae for `conflicts_with`
       class Conflicts < FormulaCop
-        MSG = <<-EOS.undent
+        MSG = <<~EOS.freeze
           Versioned formulae should not use `conflicts_with`.
           Use `keg_only :versioned_formula` instead.
         EOS