API, raw file fetching error

Created by: yangchenyun

the raw API complains about mime_type.

Started GET "/api/v2/projects/huali/repository/commits/master/blob?file_path=README.md" for 127.0.0.1 at 2012-12-18 22:03:37 +0800

NoMethodError (undefined method `mime_type' for #<Grit::Tree "d4f519f3459dc58a2757cb026bb5d91dede38f68">):
  app/models/tree.rb:5:in `mime_type'
  lib/api/projects.rb:381:in `block (2 levels) in <class:Projects>