$ git clone -n https://src.fedoraproject.org/rpms/boxes.git /var/lib/mock/f45-build-5019-337/root/chroot_tmpdir/scmroot/boxes
Cloning into '/var/lib/mock/f45-build-5019-337/root/chroot_tmpdir/scmroot/boxes'...
$ git fetch origin dd36be2eb68fd79885ab6a2d14a6b45b3f8175a4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/boxes
 * [new ref]         dd36be2eb68fd79885ab6a2d14a6b45b3f8175a4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dd36be2 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild