gitrepo warning upon push

[Ed Maste]

It looks like we have some cleanup that needs to be automated.

% git push freebsd stable/12
...
remote: warning: The last gc run reported the following. Please
correct the root cause
remote: and remove gc.log.
remote: Automatic cleanup will not be performed until the file is removed.
remote:
remote: warning: There are too many unreachable loose objects; run
'git prune' to remove them.
remote: