Loose refs not packed as often as they should on pull mirrors

From #34310 (closed), there was a fork of www-gitlab-com that had a lot of loose refs. It failed to pull because the loose ref gerir/infra/kpi conflicted with the new ref gerir/infra/kpi/targets.

I'm wondering if we have a general problem where we're calling git pack-refs without the --all flag. This might explain why we are seeing more loose refs than we would expect.

It could just be a pull mirror issue. If we aren't able to run update-refs because of a conflict branch name where a/b exists already but a/b/c is created, we may want to pack refs.