$ git clone -n https://src.fedoraproject.org/rpms/f38-backgrounds.git /var/lib/mock/f40-build-2347407-60101/root/chroot_tmpdir/scmroot/f38-backgrounds
Cloning into '/var/lib/mock/f40-build-2347407-60101/root/chroot_tmpdir/scmroot/f38-backgrounds'...
$ git fetch origin 4f202c17481de7387e48f53c16d25a2f76106be4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f38-backgrounds
 * [new ref]         4f202c17481de7387e48f53c16d25a2f76106be4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4f202c1 Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild