When pushing a package for the first time, pkgctl should consider non-committed PKGBUILD files

Doing

pkgctl repo create foo
pkgctl repo clone foo

then editing a new PKGBUILD file and doing

pkgctl build
pkgctl release -u --repo extra

leads to a

==> Releasing zsa-udev to extra
==> Signing package /home/user/.local/state/pkgctl/foo/foo-1.2.3-1-any.pkg.tar.zst...
==> Fetching remote changes
==> Releasing package
fatal: Failed to resolve 'HEAD' as a valid ref.
==> ERROR: Aborting...

I think this could be solved by either failing more nicely (and earlier) with a more descriptive message or alternatively by automatically adding/considering an uncommitted PKGBUILD file.