$ git clone -n https://src.fedoraproject.org/rpms/f23-backgrounds.git /var/lib/mock/f39-build-1463381-33424/root/chroot_tmpdir/scmroot/f23-backgrounds
Cloning into '/var/lib/mock/f39-build-1463381-33424/root/chroot_tmpdir/scmroot/f23-backgrounds'...
$ git fetch origin da04fb664d7ebd365e0b90386b0e5b033a92fcb0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/f23-backgrounds
 * [new ref]         da04fb664d7ebd365e0b90386b0e5b033a92fcb0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at da04fb6 Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild