brew/Library/Homebrew/cmd/commands.rb

module Homebrew
  def commands
    if ARGV.include? "--quiet"
      cmds = internal_commands + external_commands
      cmds += HOMEBREW_INTERNAL_COMMAND_ALIASES.keys if ARGV.include? "--include-aliases"
      puts_columns cmds.sort
    else
      # Find commands in Homebrew/cmd
      puts "Built-in commands"
      puts_columns internal_commands

      # Find commands in the path
      unless (exts = external_commands).empty?
        puts
        puts "External commands"
        puts_columns exts
      end
    end
  end

  def internal_commands
    with_directory = false
    (HOMEBREW_REPOSITORY/"Library/Homebrew/cmd").
       children(with_directory).
       map {|f| File.basename(f, '.rb')}
  end

  def external_commands
    paths.map{ |p| Dir["#{p}/brew-*"] }.flatten.
      map{ |f| File.basename(f, '.rb')[5..-1] }.
      reject{ |f| f =~ /\./ }
  end
end