I have an existing git repo (a bare one) which has up to this point only been writable by me. I want to open it up to some UNIX user group, foo, so that all members of foo can push to it. I'm aware that I can easily set up a new git repo with:
git init --bare --shared=group repodir
chgrp -R foo repodir
But I need the equivalent operation for an existing repo dir.