$ git clone -n https://src.fedoraproject.org/rpms/libmks.git /var/lib/mock/f40-build-2228017-53057/root/chroot_tmpdir/scmroot/libmks
Cloning into '/var/lib/mock/f40-build-2228017-53057/root/chroot_tmpdir/scmroot/libmks'...
$ git fetch origin dd8b58908a67436e817f5f8945d782dc1d90ecde:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libmks
 * [new ref]         dd8b58908a67436e817f5f8945d782dc1d90ecde -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dd8b589 Use supplements instead of requires for qemu