    # File lib/rubygems/commands/which_command.rb, line 8
      def initialize
        super 'which', 'Find the location of a library',
              :search_gems_first => false, :show_all => false

        add_option '-a', '--[no-]all', 'show all matching files' do |show_all, options|
          options[:show_all] = show_all
        end

        add_option '-g', '--[no-]gems-first',
                   'search gems before non-gems' do |gems_first, options|
          options[:search_gems_first] = gems_first
        end
      end