gitweb: Unable to edit repo metadata

Using Debian testing, an error 505 happens when trying to edit a repository metadata, plinth log:

   INFO plinth.actions       # gitweb..repo_info(…)                                                                                                                                                                
   ERROR plinth.actions       Error running action gitweb..repo_info(*('Test-repo-private',), **{}): Command '['git', '-C', '/var/lib/git/Test-repo-private.git', 'symbolic-ref', '--short', 'HEAD']' returned non-z
ero exit status 128. (128, ['git', '-C', '/var/lib/git/Test-repo-private.git', 'symbolic-ref', '--short', 'HEAD'], b'', b'fatal: detected dubious ownership in repository at \'/var/lib/git/Test-repo-private.git\'