Git do not ask for login/password

Git ask the user for a login/password only when it receive a 401 at the
first GET request.

If it gets a 401 at the POST, it just fails.

* app/controllers/git_http_controller.rb: Check for "service" parameter
  to detect "push".
Merge pull request #27 from baby-gnu/hotfix/git-http-check-service-parameter-for-is_push

Git do not ask for login/password
Thank you!