which_to_update (Gem::Commands::UpdateCommand)

    # File lib/rubygems/commands/update_command.rb, line 133
      def which_to_update(highest_installed_gems, remote_gemspecs)
        result = []

        highest_installed_gems.each do |l_name, l_spec|
          matching_gems = remote_gemspecs.select do |spec|
            spec.name == l_name and Gem.platforms.any? do |platform|
              platform == spec.platform
            end
          end

          highest_remote_gem = matching_gems.sort_by { |spec| spec.version }.last

          if highest_remote_gem and
             l_spec.version < highest_remote_gem.version then
            result << l_name
          end
        end

        result
      end