diff --git a/Library/Homebrew/brew.rb b/Library/Homebrew/brew.rb
index c453938981..0abb8d37b1 100644
--- a/Library/Homebrew/brew.rb
+++ b/Library/Homebrew/brew.rb
@@ -78,8 +78,8 @@ begin
   # - no arguments are passed
   # - if cmd is Cask, let Cask handle the help command instead
   if (empty_argv || help_flag) && cmd != "cask"
-    require "cmd/help"
-    Homebrew.help cmd, empty_argv: empty_argv
+    require "help"
+    Homebrew::Help.help cmd, empty_argv: empty_argv
     # `Homebrew.help` never returns, except for external/unknown commands.
   end
 
@@ -119,8 +119,8 @@ begin
     exec HOMEBREW_BREW_FILE, cmd, *ARGV
   end
 rescue UsageError => e
-  require "cmd/help"
-  Homebrew.help cmd, usage_error: e.message
+  require "help"
+  Homebrew::Help.help cmd, usage_error: e.message
 rescue SystemExit => e
   onoe "Kernel.exit" if ARGV.verbose? && !e.success?
   $stderr.puts e.backtrace if ARGV.debug?
diff --git a/Library/Homebrew/cmd/--cache.rb b/Library/Homebrew/cmd/--cache.rb
index 2c407cefe0..9298bdb455 100644
--- a/Library/Homebrew/cmd/--cache.rb
+++ b/Library/Homebrew/cmd/--cache.rb
@@ -1,10 +1,10 @@
 #:  * `--cache`:
 #:    Display Homebrew's download cache. See also `HOMEBREW_CACHE`.
 #:
-#:  * `--cache` <formula>:
+#:  * `--cache` [`--build-from-source`|`-s`] [`--force-bottle`] <formula>:
 #:    Display the file or directory used to cache <formula>.
 
-require "cmd/fetch"
+require "fetch"
 
 module Homebrew
   module_function
@@ -14,7 +14,7 @@ module Homebrew
       puts HOMEBREW_CACHE
     else
       ARGV.formulae.each do |f|
-        if fetch_bottle?(f)
+        if Fetch.fetch_bottle?(f)
           puts f.bottle.cached_download
         else
           puts f.cached_download
diff --git a/Library/Homebrew/cmd/fetch.rb b/Library/Homebrew/cmd/fetch.rb
index f150d8f16a..c518600e9c 100644
--- a/Library/Homebrew/cmd/fetch.rb
+++ b/Library/Homebrew/cmd/fetch.rb
@@ -23,6 +23,7 @@
 #:    installation.
 
 require "formula"
+require "fetch"
 
 module Homebrew
   module_function
@@ -46,7 +47,7 @@ module Homebrew
       f.print_tap_action verb: "Fetching"
 
       fetched_bottle = false
-      if fetch_bottle?(f)
+      if Fetch.fetch_bottle?(f)
         begin
           fetch_formula(f.bottle)
         rescue Interrupt
@@ -73,14 +74,6 @@ module Homebrew
     end
   end
 
-  def fetch_bottle?(f)
-    return true if ARGV.force_bottle? && f.bottle
-    return false unless f.bottle && f.pour_bottle?
-    return false if ARGV.build_formula_from_source?(f)
-    return false unless f.bottle.compatible_cellar?
-    true
-  end
-
   def fetch_resource(r)
     puts "Resource: #{r.name}"
     fetch_fetchable r
diff --git a/Library/Homebrew/cmd/help.rb b/Library/Homebrew/cmd/help.rb
index fa5727816e..84d28ab358 100644
--- a/Library/Homebrew/cmd/help.rb
+++ b/Library/Homebrew/cmd/help.rb
@@ -1,91 +1,7 @@
-HOMEBREW_HELP = <<~EOS.freeze
-  Example usage:
-    brew search [TEXT|/REGEX/]
-    brew info [FORMULA...]
-    brew install FORMULA...
-    brew update
-    brew upgrade [FORMULA...]
-    brew uninstall FORMULA...
-    brew list [FORMULA...]
-
-  Troubleshooting:
-    brew config
-    brew doctor
-    brew install --verbose --debug FORMULA
-
-  Contributing:
-    brew create [URL [--no-fetch]]
-    brew edit [FORMULA...]
-
-  Further help:
-    brew commands
-    brew help [COMMAND]
-    man brew
-    https://docs.brew.sh
-EOS
-
-# NOTE Keep the lenth of vanilla --help less than 25 lines!
-# This is because the default Terminal height is 25 lines. Scrolling sucks
-# and concision is important. If more help is needed we should start
-# specialising help like the gem command does.
-# NOTE Keep lines less than 80 characters! Wrapping is just not cricket.
-# NOTE The reason the string is at the top is so 25 lines is easy to measure!
-
-require "commands"
+require "help"
 
 module Homebrew
-  module_function
-
   def help(cmd = nil, flags = {})
-    # Resolve command aliases and find file containing the implementation.
-    if cmd
-      cmd = HOMEBREW_INTERNAL_COMMAND_ALIASES.fetch(cmd, cmd)
-      path = Commands.path(cmd)
-      path ||= which("brew-#{cmd}")
-      path ||= which("brew-#{cmd}.rb")
-    end
-
-    # Display command-specific (or generic) help in response to `UsageError`.
-    if (error_message = flags[:usage_error])
-      $stderr.puts path ? command_help(path) : HOMEBREW_HELP
-      $stderr.puts
-      onoe error_message
-      exit 1
-    end
-
-    # Handle `brew` (no arguments).
-    if flags[:empty_argv]
-      $stderr.puts HOMEBREW_HELP
-      exit 1
-    end
-
-    # Handle `brew (-h|--help|--usage|-?|help)` (no other arguments).
-    if cmd.nil?
-      puts HOMEBREW_HELP
-      exit 0
-    end
-
-    # Resume execution in `brew.rb` for unknown commands.
-    return if path.nil?
-
-    # Display help for internal command (or generic help if undocumented).
-    puts command_help(path)
-    exit 0
-  end
-
-  def command_help(path)
-    help_lines = command_help_lines(path)
-    if help_lines.empty?
-      opoo "No help text in: #{path}" if ARGV.homebrew_developer?
-      HOMEBREW_HELP
-    else
-      help_lines.map do |line|
-        line.sub(/^  \* /, "#{Tty.bold}brew#{Tty.reset} ")
-            .gsub(/`(.*?)`/, "#{Tty.bold}\\1#{Tty.reset}")
-            .gsub(%r{<([^\s]+?://[^\s]+?)>}) { |url| Formatter.url(url) }
-            .gsub(/<(.*?)>/, "#{Tty.underline}\\1#{Tty.reset}")
-            .gsub("@hide_from_man_page", "")
-      end.join.strip
-    end
+    Help.help(cmd, flags)
   end
 end
diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index 21ea88193a..4b699474e1 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -68,11 +68,10 @@
 #:    creating patches to the software.
 
 require "missing_formula"
-require "diagnostic"
 require "cmd/search"
 require "formula_installer"
-require "hardware"
 require "development_tools"
+require "install"
 
 module Homebrew
   module_function
@@ -238,7 +237,7 @@ module Homebrew
       end
 
       return if formulae.empty?
-      perform_preinstall_checks
+      Install.perform_preinstall_checks
 
       formulae.each do |f|
         Migrator.migrate_if_needed(f)
@@ -298,47 +297,6 @@ module Homebrew
     end
   end
 
-  def check_ppc
-    case Hardware::CPU.type
-    when :ppc
-      abort <<~EOS
-        Sorry, Homebrew does not support your computer's CPU architecture.
-        For PPC support, see: https://github.com/mistydemeo/tigerbrew
-      EOS
-    end
-  end
-
-  def check_writable_install_location
-    raise "Cannot write to #{HOMEBREW_CELLAR}" if HOMEBREW_CELLAR.exist? && !HOMEBREW_CELLAR.writable_real?
-    raise "Cannot write to #{HOMEBREW_PREFIX}" unless HOMEBREW_PREFIX.writable_real? || HOMEBREW_PREFIX.to_s == "/usr/local"
-  end
-
-  def check_development_tools
-    checks = Diagnostic::Checks.new
-    checks.fatal_development_tools_checks.each do |check|
-      out = checks.send(check)
-      next if out.nil?
-      ofail out
-    end
-    exit 1 if Homebrew.failed?
-  end
-
-  def check_cellar
-    FileUtils.mkdir_p HOMEBREW_CELLAR unless File.exist? HOMEBREW_CELLAR
-  rescue
-    raise <<~EOS
-      Could not create #{HOMEBREW_CELLAR}
-      Check you have permission to write to #{HOMEBREW_CELLAR.parent}
-    EOS
-  end
-
-  def perform_preinstall_checks
-    check_ppc
-    check_writable_install_location
-    check_development_tools if DevelopmentTools.installed?
-    check_cellar
-  end
-
   def install_formula(f)
     f.print_tap_action
     build_options = f.build
diff --git a/Library/Homebrew/cmd/link.rb b/Library/Homebrew/cmd/link.rb
index 5afb19ed61..a412ca2f52 100644
--- a/Library/Homebrew/cmd/link.rb
+++ b/Library/Homebrew/cmd/link.rb
@@ -26,7 +26,7 @@ module Homebrew
     mode.dry_run = true if ARGV.dry_run?
 
     ARGV.kegs.each do |keg|
-      keg_only = keg_only?(keg.rack)
+      keg_only = Formulary.keg_only?(keg.rack)
       if HOMEBREW_PREFIX.to_s == "/usr/local" && keg_only &&
          keg.name.start_with?("openssl", "libressl")
         opoo <<~EOS
@@ -87,10 +87,4 @@ module Homebrew
     puts "  #{Utils::Shell.prepend_path_in_profile(opt/"bin")}"  if bin.directory?
     puts "  #{Utils::Shell.prepend_path_in_profile(opt/"sbin")}" if sbin.directory?
   end
-
-  def keg_only?(rack)
-    Formulary.from_rack(rack).keg_only?
-  rescue FormulaUnavailableError, TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError
-    false
-  end
 end
diff --git a/Library/Homebrew/cmd/style.rb b/Library/Homebrew/cmd/style.rb
index 7487c51214..5a050d1cd0 100644
--- a/Library/Homebrew/cmd/style.rb
+++ b/Library/Homebrew/cmd/style.rb
@@ -21,6 +21,7 @@
 
 require "json"
 require "open3"
+require "style"
 
 module Homebrew
   module_function
@@ -53,153 +54,6 @@ module Homebrew
                                  NewFormulaAudit]
     end
 
-    Homebrew.failed = check_style_and_print(target, options)
-  end
-
-  # Checks style for a list of files, printing simple RuboCop output.
-  # Returns true if violations were found, false otherwise.
-  def check_style_and_print(files, options = {})
-    check_style_impl(files, :print, options)
-  end
-
-  # Checks style for a list of files, returning results as a RubocopResults
-  # object parsed from its JSON output.
-  def check_style_json(files, options = {})
-    check_style_impl(files, :json, options)
-  end
-
-  def check_style_impl(files, output_type, options = {})
-    fix = options[:fix]
-
-    Homebrew.install_gem_setup_path! "rubocop", HOMEBREW_RUBOCOP_VERSION
-    require "rubocop"
-    require_relative "../rubocops"
-
-    args = %w[
-      --force-exclusion
-    ]
-    if fix
-      args << "--auto-correct"
-    else
-      args << "--parallel"
-    end
-
-    if ARGV.include?("--rspec")
-      Homebrew.install_gem! "rubocop-rspec"
-      args += %w[--require rubocop-rspec]
-    end
-
-    if options[:except_cops]
-      options[:except_cops].map! { |cop| RuboCop::Cop::Cop.registry.qualified_cop_name(cop.to_s, "") }
-      cops_to_exclude = options[:except_cops].select do |cop|
-        RuboCop::Cop::Cop.registry.names.include?(cop) ||
-          RuboCop::Cop::Cop.registry.departments.include?(cop.to_sym)
-      end
-
-      args << "--except" << cops_to_exclude.join(",") unless cops_to_exclude.empty?
-    elsif options[:only_cops]
-      options[:only_cops].map! { |cop| RuboCop::Cop::Cop.registry.qualified_cop_name(cop.to_s, "") }
-      cops_to_include = options[:only_cops].select do |cop|
-        RuboCop::Cop::Cop.registry.names.include?(cop) ||
-          RuboCop::Cop::Cop.registry.departments.include?(cop.to_sym)
-      end
-
-      if cops_to_include.empty?
-        odie "RuboCops #{options[:only_cops].join(",")} were not found"
-      end
-
-      args << "--only" << cops_to_include.join(",")
-    end
-
-    if files.nil?
-      config_file = ARGV.include?("--rspec") ? ".rubocop-rspec.yml" : ".rubocop.yml"
-      args << "--config" << HOMEBREW_LIBRARY_PATH/config_file
-      args << HOMEBREW_LIBRARY_PATH
-    else
-      args << "--config" << HOMEBREW_LIBRARY/".rubocop_audit.yml"
-      args += files
-    end
-
-    cache_env = { "XDG_CACHE_HOME" => "#{HOMEBREW_CACHE}/style" }
-
-    case output_type
-    when :print
-      args << "--debug" if ARGV.debug?
-      args << "--display-cop-names" if ARGV.include? "--display-cop-names"
-      args << "--format" << "simple" if files
-      system(cache_env, "rubocop", "_#{HOMEBREW_RUBOCOP_VERSION}_", *args)
-      !$CHILD_STATUS.success?
-    when :json
-      json, _, status = Open3.capture3(cache_env, "rubocop", "_#{HOMEBREW_RUBOCOP_VERSION}_", "--format", "json", *args)
-      # exit status of 1 just means violations were found; other numbers mean
-      # execution errors.
-      # exitstatus can also be nil if RuboCop process crashes, e.g. due to
-      # native extension problems.
-      # JSON needs to be at least 2 characters.
-      if !(0..1).cover?(status.exitstatus) || json.to_s.length < 2
-        raise "Error running `rubocop --format json #{args.join " "}`"
-      end
-      RubocopResults.new(JSON.parse(json))
-    else
-      raise "Invalid output_type for check_style_impl: #{output_type}"
-    end
-  end
-
-  class RubocopResults
-    def initialize(json)
-      @metadata = json["metadata"]
-      @file_offenses = {}
-      json["files"].each do |f|
-        next if f["offenses"].empty?
-        file = File.realpath(f["path"])
-        @file_offenses[file] = f["offenses"].map { |x| RubocopOffense.new(x) }
-      end
-    end
-
-    def file_offenses(path)
-      @file_offenses[path.to_s]
-    end
-  end
-
-  class RubocopOffense
-    attr_reader :severity, :message, :corrected, :location, :cop_name
-
-    def initialize(json)
-      @severity = json["severity"]
-      @message = json["message"]
-      @cop_name = json["cop_name"]
-      @corrected = json["corrected"]
-      @location = RubocopLineLocation.new(json["location"])
-    end
-
-    def severity_code
-      @severity[0].upcase
-    end
-
-    def to_s(options = {})
-      if options[:display_cop_name]
-        "#{severity_code}: #{location.to_short_s}: #{cop_name}: #{message}"
-      else
-        "#{severity_code}: #{location.to_short_s}: #{message}"
-      end
-    end
-  end
-
-  class RubocopLineLocation
-    attr_reader :line, :column, :length
-
-    def initialize(json)
-      @line = json["line"]
-      @column = json["column"]
-      @length = json["length"]
-    end
-
-    def to_s
-      "#{line}: col #{column} (#{length} chars)"
-    end
-
-    def to_short_s
-      "#{line}: col #{column}"
-    end
+    Homebrew.failed = Style.check_style_and_print(target, options)
   end
 end
diff --git a/Library/Homebrew/cmd/switch.rb b/Library/Homebrew/cmd/switch.rb
index b0ac32626e..1393e3052f 100644
--- a/Library/Homebrew/cmd/switch.rb
+++ b/Library/Homebrew/cmd/switch.rb
@@ -3,7 +3,6 @@
 
 require "formula"
 require "keg"
-require "cmd/link"
 
 module Homebrew
   module_function
@@ -53,7 +52,7 @@ module Homebrew
     keg = Keg.new(rack/version)
 
     # Link new version, if not keg-only
-    if keg_only?(rack)
+    if Formulary.keg_only?(rack)
       keg.optlink
       puts "Opt link created for #{keg}"
     else
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index 340037a2ba..9023451013 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -17,7 +17,8 @@
 #:    If <formulae> are given, upgrade only the specified brews (unless they
 #:    are pinned; see `pin`, `unpin`).
 
-require "cmd/install"
+require "install"
+require "formula_installer"
 require "cleanup"
 require "development_tools"
 
@@ -27,7 +28,7 @@ module Homebrew
   def upgrade
     FormulaInstaller.prevent_build_flags unless DevelopmentTools.installed?
 
-    Homebrew.perform_preinstall_checks
+    Install.perform_preinstall_checks
 
     odisabled "'brew upgrade --all'", "'brew upgrade'" if ARGV.include?("--all")
 
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 61cede8f27..2352fd0b4f 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -43,7 +43,7 @@ require "utils/curl"
 require "extend/ENV"
 require "formula_cellar_checks"
 require "cmd/search"
-require "cmd/style"
+require "style"
 require "date"
 require "missing_formula"
 require "digest"
@@ -116,7 +116,7 @@ module Homebrew
 
     options[:display_cop_names] = args.display_cop_names?
     # Check style in a single batch run up front for performance
-    style_results = check_style_json(files, options)
+    style_results = Style.check_style_json(files, options)
 
     new_formula_problem_lines = []
     ff.sort.each do |f|
diff --git a/Library/Homebrew/fetch.rb b/Library/Homebrew/fetch.rb
new file mode 100644
index 0000000000..ca060a36c3
--- /dev/null
+++ b/Library/Homebrew/fetch.rb
@@ -0,0 +1,13 @@
+module Homebrew
+  module Fetch
+    module_function
+
+    def fetch_bottle?(f)
+      return true if ARGV.force_bottle? && f.bottle
+      return false unless f.bottle && f.pour_bottle?
+      return false if ARGV.build_formula_from_source?(f)
+      return false unless f.bottle.compatible_cellar?
+      true
+    end
+  end
+end
diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index eab57183bc..112b296dc4 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -298,6 +298,13 @@ module Formulary
     end
   end
 
+  # Return whether given rack is keg-only
+  def self.keg_only?(rack)
+    Formulary.from_rack(rack).keg_only?
+  rescue FormulaUnavailableError, TapFormulaAmbiguityError, TapFormulaWithOldnameAmbiguityError
+    false
+  end
+
   # Return a Formula instance for the given keg.
   # It will auto resolve formula's spec when requested spec is nil
   def self.from_keg(keg, spec = nil, alias_path: nil)
diff --git a/Library/Homebrew/help.rb b/Library/Homebrew/help.rb
new file mode 100644
index 0000000000..76ddbb79e9
--- /dev/null
+++ b/Library/Homebrew/help.rb
@@ -0,0 +1,93 @@
+HOMEBREW_HELP = <<~EOS.freeze
+  Example usage:
+    brew search [TEXT|/REGEX/]
+    brew info [FORMULA...]
+    brew install FORMULA...
+    brew update
+    brew upgrade [FORMULA...]
+    brew uninstall FORMULA...
+    brew list [FORMULA...]
+
+  Troubleshooting:
+    brew config
+    brew doctor
+    brew install --verbose --debug FORMULA
+
+  Contributing:
+    brew create [URL [--no-fetch]]
+    brew edit [FORMULA...]
+
+  Further help:
+    brew commands
+    brew help [COMMAND]
+    man brew
+    https://docs.brew.sh
+EOS
+
+# NOTE Keep the length of vanilla --help less than 25 lines!
+# This is because the default Terminal height is 25 lines. Scrolling sucks
+# and concision is important. If more help is needed we should start
+# specialising help like the gem command does.
+# NOTE Keep lines less than 80 characters! Wrapping is just not cricket.
+# NOTE The reason the string is at the top is so 25 lines is easy to measure!
+
+require "commands"
+
+module Homebrew
+  module Help
+    module_function
+
+    def help(cmd = nil, flags = {})
+      # Resolve command aliases and find file containing the implementation.
+      if cmd
+        cmd = HOMEBREW_INTERNAL_COMMAND_ALIASES.fetch(cmd, cmd)
+        path = Commands.path(cmd)
+        path ||= which("brew-#{cmd}")
+        path ||= which("brew-#{cmd}.rb")
+      end
+
+      # Display command-specific (or generic) help in response to `UsageError`.
+      if (error_message = flags[:usage_error])
+        $stderr.puts path ? command_help(path) : HOMEBREW_HELP
+        $stderr.puts
+        onoe error_message
+        exit 1
+      end
+
+      # Handle `brew` (no arguments).
+      if flags[:empty_argv]
+        $stderr.puts HOMEBREW_HELP
+        exit 1
+      end
+
+      # Handle `brew (-h|--help|--usage|-?|help)` (no other arguments).
+      if cmd.nil?
+        puts HOMEBREW_HELP
+        exit 0
+      end
+
+      # Resume execution in `brew.rb` for unknown commands.
+      return if path.nil?
+
+      # Display help for internal command (or generic help if undocumented).
+      puts command_help(path)
+      exit 0
+    end
+
+    def command_help(path)
+      help_lines = command_help_lines(path)
+      if help_lines.empty?
+        opoo "No help text in: #{path}" if ARGV.homebrew_developer?
+        HOMEBREW_HELP
+      else
+        help_lines.map do |line|
+          line.sub(/^  \* /, "#{Tty.bold}brew#{Tty.reset} ")
+              .gsub(/`(.*?)`/, "#{Tty.bold}\\1#{Tty.reset}")
+              .gsub(%r{<([^\s]+?://[^\s]+?)>}) { |url| Formatter.url(url) }
+              .gsub(/<(.*?)>/, "#{Tty.underline}\\1#{Tty.reset}")
+              .gsub("@hide_from_man_page", "")
+        end.join.strip
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/install.rb b/Library/Homebrew/install.rb
new file mode 100644
index 0000000000..f426db2b09
--- /dev/null
+++ b/Library/Homebrew/install.rb
@@ -0,0 +1,54 @@
+require "diagnostic"
+require "fileutils"
+require "hardware"
+require "development_tools"
+
+module Homebrew
+  module Install
+    module_function
+
+    def check_ppc
+      case Hardware::CPU.type
+      when :ppc
+        abort <<~EOS
+          Sorry, Homebrew does not support your computer's CPU architecture.
+          For PPC support, see: https://github.com/mistydemeo/tigerbrew
+        EOS
+      end
+    end
+
+    def check_writable_install_location
+      if HOMEBREW_CELLAR.exist? && !HOMEBREW_CELLAR.writable_real?
+        raise "Cannot write to #{HOMEBREW_CELLAR}"
+      end
+      prefix_writable = HOMEBREW_PREFIX.writable_real? || HOMEBREW_PREFIX.to_s == "/usr/local"
+      raise "Cannot write to #{HOMEBREW_PREFIX}" unless prefix_writable
+    end
+
+    def check_development_tools
+      checks = Diagnostic::Checks.new
+      checks.fatal_development_tools_checks.each do |check|
+        out = checks.send(check)
+        next if out.nil?
+        ofail out
+      end
+      exit 1 if Homebrew.failed?
+    end
+
+    def check_cellar
+      FileUtils.mkdir_p HOMEBREW_CELLAR unless File.exist? HOMEBREW_CELLAR
+    rescue
+      raise <<~EOS
+        Could not create #{HOMEBREW_CELLAR}
+        Check you have permission to write to #{HOMEBREW_CELLAR.parent}
+      EOS
+    end
+
+    def perform_preinstall_checks
+      check_ppc
+      check_writable_install_location
+      check_development_tools if DevelopmentTools.installed?
+      check_cellar
+    end
+  end
+end
diff --git a/Library/Homebrew/style.rb b/Library/Homebrew/style.rb
new file mode 100644
index 0000000000..acd3be45c1
--- /dev/null
+++ b/Library/Homebrew/style.rb
@@ -0,0 +1,152 @@
+module Homebrew
+  module Style
+    module_function
+
+    # Checks style for a list of files, printing simple RuboCop output.
+    # Returns true if violations were found, false otherwise.
+    def check_style_and_print(files, options = {})
+      check_style_impl(files, :print, options)
+    end
+
+    # Checks style for a list of files, returning results as a RubocopResults
+    # object parsed from its JSON output.
+    def check_style_json(files, options = {})
+      check_style_impl(files, :json, options)
+    end
+
+    def check_style_impl(files, output_type, options = {})
+      fix = options[:fix]
+
+      Homebrew.install_gem_setup_path! "rubocop", HOMEBREW_RUBOCOP_VERSION
+      require "rubocop"
+      require "rubocops"
+
+      args = %w[
+        --force-exclusion
+      ]
+      if fix
+        args << "--auto-correct"
+      else
+        args << "--parallel"
+      end
+
+      if ARGV.include?("--rspec")
+        Homebrew.install_gem! "rubocop-rspec"
+        args += %w[--require rubocop-rspec]
+      end
+
+      if options[:except_cops]
+        options[:except_cops].map! { |cop| RuboCop::Cop::Cop.registry.qualified_cop_name(cop.to_s, "") }
+        cops_to_exclude = options[:except_cops].select do |cop|
+          RuboCop::Cop::Cop.registry.names.include?(cop) ||
+            RuboCop::Cop::Cop.registry.departments.include?(cop.to_sym)
+        end
+
+        args << "--except" << cops_to_exclude.join(",") unless cops_to_exclude.empty?
+      elsif options[:only_cops]
+        options[:only_cops].map! { |cop| RuboCop::Cop::Cop.registry.qualified_cop_name(cop.to_s, "") }
+        cops_to_include = options[:only_cops].select do |cop|
+          RuboCop::Cop::Cop.registry.names.include?(cop) ||
+            RuboCop::Cop::Cop.registry.departments.include?(cop.to_sym)
+        end
+
+        if cops_to_include.empty?
+          odie "RuboCops #{options[:only_cops].join(",")} were not found"
+        end
+
+        args << "--only" << cops_to_include.join(",")
+      end
+
+      if files.nil?
+        config_file = ARGV.include?("--rspec") ? ".rubocop-rspec.yml" : ".rubocop.yml"
+        args << "--config" << HOMEBREW_LIBRARY_PATH/config_file
+        args << HOMEBREW_LIBRARY_PATH
+      else
+        args << "--config" << HOMEBREW_LIBRARY/".rubocop_audit.yml"
+        args += files
+      end
+
+      cache_env = { "XDG_CACHE_HOME" => "#{HOMEBREW_CACHE}/style" }
+
+      case output_type
+      when :print
+        args << "--debug" if ARGV.debug?
+        args << "--display-cop-names" if ARGV.include? "--display-cop-names"
+        args << "--format" << "simple" if files
+        system(cache_env, "rubocop", "_#{HOMEBREW_RUBOCOP_VERSION}_", *args)
+        !$CHILD_STATUS.success?
+      when :json
+        json, _, status = Open3.capture3(cache_env, "rubocop", "_#{HOMEBREW_RUBOCOP_VERSION}_", "--format", "json", *args)
+        # exit status of 1 just means violations were found; other numbers mean
+        # execution errors.
+        # exitstatus can also be nil if RuboCop process crashes, e.g. due to
+        # native extension problems.
+        # JSON needs to be at least 2 characters.
+        if !(0..1).cover?(status.exitstatus) || json.to_s.length < 2
+          raise "Error running `rubocop --format json #{args.join " "}`"
+        end
+        RubocopResults.new(JSON.parse(json))
+      else
+        raise "Invalid output_type for check_style_impl: #{output_type}"
+      end
+    end
+
+    class RubocopResults
+      def initialize(json)
+        @metadata = json["metadata"]
+        @file_offenses = {}
+        json["files"].each do |f|
+          next if f["offenses"].empty?
+          file = File.realpath(f["path"])
+          @file_offenses[file] = f["offenses"].map { |x| RubocopOffense.new(x) }
+        end
+      end
+
+      def file_offenses(path)
+        @file_offenses[path.to_s]
+      end
+    end
+
+    class RubocopOffense
+      attr_reader :severity, :message, :corrected, :location, :cop_name
+
+      def initialize(json)
+        @severity = json["severity"]
+        @message = json["message"]
+        @cop_name = json["cop_name"]
+        @corrected = json["corrected"]
+        @location = RubocopLineLocation.new(json["location"])
+      end
+
+      def severity_code
+        @severity[0].upcase
+      end
+
+      def to_s(options = {})
+        if options[:display_cop_name]
+          "#{severity_code}: #{location.to_short_s}: #{cop_name}: #{message}"
+        else
+          "#{severity_code}: #{location.to_short_s}: #{message}"
+        end
+      end
+    end
+
+    class RubocopLineLocation
+      attr_reader :line, :column, :length
+
+      def initialize(json)
+        @line = json["line"]
+        @column = json["column"]
+        @length = json["length"]
+      end
+
+      def to_s
+        "#{line}: col #{column} (#{length} chars)"
+      end
+
+      def to_short_s
+        "#{line}: col #{column}"
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/test/cmd/style_spec.rb b/Library/Homebrew/test/cmd/style_spec.rb
index ec0eccdff1..c8ccbfbac8 100644
--- a/Library/Homebrew/test/cmd/style_spec.rb
+++ b/Library/Homebrew/test/cmd/style_spec.rb
@@ -25,7 +25,7 @@ describe "brew style" do
         end
       EOS
 
-      rubocop_result = Homebrew.check_style_json([formula])
+      rubocop_result = Homebrew::Style.check_style_json([formula])
 
       expect(rubocop_result.file_offenses(formula.realpath.to_s).map(&:message))
         .to include("Extra empty line detected at class body beginning.")
diff --git a/docs/Manpage.md b/docs/Manpage.md
index cf94d6ede4..fe58e52db5 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -597,7 +597,7 @@ With `--verbose` or `-v`, many commands print extra debugging information. Note
   * `--cache`:
     Display Homebrew's download cache. See also `HOMEBREW_CACHE`.
 
-  * `--cache` `formula`:
+  * `--cache` [`--build-from-source`|`-s`] [`--force-bottle`] `formula`:
     Display the file or directory used to cache `formula`.
 
   * `--cellar`:
diff --git a/manpages/brew-cask.1 b/manpages/brew-cask.1
index 1b2c9fae75..efe64e5988 100644
--- a/manpages/brew-cask.1
+++ b/manpages/brew-cask.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW\-CASK" "1" "May 2018" "Homebrew" "brew-cask"
+.TH "BREW\-CASK" "1" "June 2018" "Homebrew" "brew-cask"
 .
 .SH "NAME"
 \fBbrew\-cask\fR \- a friendly binary installer for macOS
diff --git a/manpages/brew.1 b/manpages/brew.1
index ac0c4b8e85..ee8c04b94a 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BREW" "1" "May 2018" "Homebrew" "brew"
+.TH "BREW" "1" "June 2018" "Homebrew" "brew"
 .
 .SH "NAME"
 \fBbrew\fR \- The missing package manager for macOS
@@ -610,7 +610,7 @@ By default, \fBuses\fR shows usage of \fIformulae\fR by stable builds\. To find
 Display Homebrew\'s download cache\. See also \fBHOMEBREW_CACHE\fR\.
 .
 .TP
-\fB\-\-cache\fR \fIformula\fR
+\fB\-\-cache\fR [\fB\-\-build\-from\-source\fR|\fB\-s\fR] [\fB\-\-force\-bottle\fR] \fIformula\fR
 Display the file or directory used to cache \fIformula\fR\.
 .
 .TP