# File lib/action_view/helpers/asset_tag_helper.rb, line 492
      def stylesheet_link_tag(*sources)
        options = sources.extract_options!.stringify_keys
        concat  = options.delete("concat")
        cache   = concat || options.delete("cache")
        recursive = options.delete("recursive")

        if concat || (config.perform_caching && cache)
          joined_stylesheet_name = (cache == true ? "all" : cache) + ".css"
          joined_stylesheet_path = File.join(joined_stylesheet_name[/^#{File::SEPARATOR}/] ? config.assets_dir : config.stylesheets_dir, joined_stylesheet_name)

          unless config.perform_caching && File.exists?(joined_stylesheet_path)
            write_asset_file_contents(joined_stylesheet_path, compute_stylesheet_paths(sources, recursive))
          end
          stylesheet_tag(joined_stylesheet_name, options)
        else
          sources = expand_stylesheet_sources(sources, recursive)
          ensure_stylesheet_sources!(sources) if cache
          sources.collect { |source| stylesheet_tag(source, options) }.join("\n").html_safe
        end
      end