$ git clone -n https://src.fedoraproject.org/rpms/f35-backgrounds.git /var/lib/mock/f45-build-8602-391/root/chroot_tmpdir/scmroot/f35-backgrounds
Cloning into '/var/lib/mock/f45-build-8602-391/root/chroot_tmpdir/scmroot/f35-backgrounds'...
$ git fetch origin 8f5d4eae3d0b467976b9d0d6bcb20b6f3a179ee0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f35-backgrounds
 * [new ref]         8f5d4eae3d0b467976b9d0d6bcb20b6f3a179ee0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8f5d4ea Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild