Default branch is not set in HEAD of bare repository

Created by: simonswine

This issue is similar to #2572, which was never fixed.

If you change the default branch in gitlab, this settings should also be set in the bare git repository. This can be done with this command: git symbolic-ref HEAD refs/heads/new_default_branch.

Without this fix i'm not able to delete a remote master branch, although it isn't the default branch (in gitlab) anymore