$ git clone -n https://src.fedoraproject.org/rpms/f37-backgrounds.git /var/lib/mock/f45-build-8607-392/root/chroot_tmpdir/scmroot/f37-backgrounds
Cloning into '/var/lib/mock/f45-build-8607-392/root/chroot_tmpdir/scmroot/f37-backgrounds'...
$ git fetch origin 5b12fa52badcb31cae4ca55b1046b198fd9f4607:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f37-backgrounds
 * [new ref]         5b12fa52badcb31cae4ca55b1046b198fd9f4607 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5b12fa5 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild