$ git clone -n https://src.fedoraproject.org/rpms/mmg.git /var/lib/mock/f45-build-18997-539/root/chroot_tmpdir/scmroot/mmg
Cloning into '/var/lib/mock/f45-build-18997-539/root/chroot_tmpdir/scmroot/mmg'...
$ git fetch origin fc71b67c39cfa512d5ec100d173965e37455c00d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mmg
 * [new ref]         fc71b67c39cfa512d5ec100d173965e37455c00d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fc71b67 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild