handle attahcment with send_file

config/routes.rb

@@ -45,6 +45,11 @@ Gitlab::Application.routes.draw do
     root to: "projects#index"
   end
 
+  #
+  # Attachments serving
+  #
+  get 'files/:type/:id/:filename' => 'files#download', constraints: { id: /\d+/, type: /[a-z]+/, filename: /[a-zA-Z.0-9_\-\+]+/ }
+
   #
   # Admin Area
   #