$ git clone -n https://src.fedoraproject.org/rpms/mfem.git /var/lib/mock/f39-build-1660947-40652/root/chroot_tmpdir/scmroot/mfem
Cloning into '/var/lib/mock/f39-build-1660947-40652/root/chroot_tmpdir/scmroot/mfem'...
$ git fetch origin cdbf13b75f4fdfe8b61cc5321f57ed2268ec7ef5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mfem
 * [new ref]         cdbf13b75f4fdfe8b61cc5321f57ed2268ec7ef5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cdbf13b Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild