Regression in v2.13.3, fixed in master: aliases in worktrees

Hi all,

just to let you know that repository-local aliases stopped working in v2.13.3. This is due to my "aliases via early config" work that made it into a maintenance release...

The bug is fixed in master already, and I cherry-picked Brandon's config-h series that contains the fix into Git for Windows' master branch.

I only had to add one add-on patch that falls back to opts->git_dir when opts->commondir is NULL (no idea whether that can happen in Git's master, but it can happen in Git for Windows' master at least).

It *may* be worth it to cherry-pick this to `maint`, too, but then, it looks as if I am the only really serious user of worktrees anyway (given that auto-gc still corrupts worktrees' reflogs, and it is a known bug for 2 years and counting).

So I dunno. Maybe not worth bothering about in `maint`. Less work for you, Junio.

Ciao, Johannes