$ git clone -n https://src.fedoraproject.org/rpms/mfem.git /var/lib/mock/f41-build-59226673-6571984/root/chroot_tmpdir/scmroot/mfem
Cloning into '/var/lib/mock/f41-build-59226673-6571984/root/chroot_tmpdir/scmroot/mfem'...
$ git fetch origin bfa760503e2f976164c9f3f70b2e69daa0dbe43b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mfem
 * [new ref]         bfa760503e2f976164c9f3f70b2e69daa0dbe43b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bfa7605 4.8