instance method builder

# File railties/lib/rails/generators/rails/app/app_generator.rb, line 319
      def builder
        @builder ||= begin
          if path = options[:builder]
            if URI(path).is_a?(URI::HTTP)
              contents = open(path, "Accept" => "application/x-thor-template") {|io| io.read }
            else
              contents = open(File.expand_path(path, @original_wd)) {|io| io.read }
            end

            prok = eval("proc { #{contents} }", TOPLEVEL_BINDING, path, 1)
            instance_eval(&prok)
          end

          builder_class = defined?(::AppBuilder) ? ::AppBuilder : Rails::AppBuilder
          builder_class.send(:include, ActionMethods)
          builder_class.new(self)
        end
      end