Git Lock file causing build to fail

I'm not sure yet how it got in this state, but at some point clearly the git process crashed, and it left the lock file in place.

I wonder if the runner could detect this and fix it, by removing the lock file.

gitlab-ci-multi-runner 1.1.1 (a127706)
Using Shell executor...
Running on gitlab-ci-runner.local...
Fetching changes...
error: update_ref failed for ref 'HEAD': cannot lock ref 'HEAD': Unable to create '/Users/gitlab2/builds/844ec43a/0/xxx/xxx/.git/HEAD.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue.