'git maintenance' won't work on bare repos

Hello,

Because we have a fairly large repository, our developers rely on
worktrees created off a bare mirror clone. I'd like to enable
maintenance, and since the worktrees are rather short-lived instances,
we cannot point 'git maintenance' to it.
So the proper solution is to do it from the bare clone itself.
However, 'git maintenance register' silently fails (with an 0 exit
code). There are two tell-tale signs:
1. 'git config --global --get maintenance.repo' returns '.'
2. There are no Crontab entries inserted.

Running 'git maintenance register' from a worktree created off the bare clone works as expected.

To reproduce: git init --bare test-me git -C test-me maintenance register git config --global --get maintenance.repo

The workaround, for now, is to run this from a worktree, then use 'git config' to reset to the corresponding bare clone location.

Thanks,

Clément