# File lib/action_controller/metal/conditional_get.rb, line 26
    def fresh_when(options)
      options.assert_valid_keys(:etag, :last_modified, :public)

      response.etag          = options[:etag]          if options[:etag]
      response.last_modified = options[:last_modified] if options[:last_modified]
      response.cache_control[:public] = true if options[:public]

      head :not_modified if request.fresh?(response)
    end