Handle tmp refs properly

We create refs inside refs/tmp/ in most cases we remove them afterwords but in this case https://gitlab.com/gitlab-org/gitlab-ce/blob/1bf57b75119deb79f5826245d4c69a0a83cc4864/app/services/compare_service.rb#L19 we don't. These refs are not a big problem by themselves but they prevent git gc from removing unnecessary objects as they hold references.

Proposed TODO:

  • Handle them properly in this case. Remove them
  • Create a rake task to remove old ones

CE repo in GitLab.com contains 2439 of these references.

/cc @dzaporozhets @pcarranza

Edited by Valery Sizov