class Gem::Commands::CleanupCommand

def execute
  say "Cleaning up installed gems..."
  primary_gems = {}
  Gem::Specification.each do |spec|
    if primary_gems[spec.name].nil? or
       primary_gems[spec.name].version < spec.version then
      primary_gems[spec.name] = spec
    end
  end
  gems_to_cleanup = unless options[:args].empty? then
                      options[:args].map do |gem_name|
                        Gem::Specification.find_all_by_name gem_name
                      end.flatten
                    else
                      Gem::Specification.to_a
                    end
  gems_to_cleanup = gems_to_cleanup.select { |spec|
    primary_gems[spec.name].version != spec.version
  }
  full = Gem::DependencyList.from_specs
  deplist = Gem::DependencyList.new
  gems_to_cleanup.uniq.each do |spec| deplist.add spec end
  deps = deplist.strongly_connected_components.flatten.reverse
  original_home = Gem.dir
  original_path = Gem.path
  deps.each do |spec|
    next unless full.ok_to_remove?(spec.full_name)
    if options[:dryrun] then
      say "Dry Run Mode: Would uninstall #{spec.full_name}"
    else
      say "Attempting to uninstall #{spec.full_name}"
      options[:args] = [spec.name]
      uninstall_options = {
        :executables => false,
        :version => "= #{spec.version}",
      }
      uninstall_options[:user_install] = Gem.user_dir == spec.base_dir
      uninstaller = Gem::Uninstaller.new spec.name, uninstall_options
      begin
        uninstaller.uninstall
      rescue Gem::DependencyRemovalException, Gem::InstallError,
             Gem::GemNotInHomeException, Gem::FilePermissionError => e
        say "Unable to uninstall #{spec.full_name}:"
        say "\t#{e.class}: #{e.message}"
      end
    end
    # Restore path Gem::Uninstaller may have change
    Gem.use_paths(original_home, *original_path)
  end
  say "Clean Up Complete"
end