$ git clone -n https://src.fedoraproject.org/rpms/ocaml-bos.git /var/lib/mock/f40-build-784452-133438/root/chroot_tmpdir/scmroot/ocaml-bos
Cloning into '/var/lib/mock/f40-build-784452-133438/root/chroot_tmpdir/scmroot/ocaml-bos'...
$ git fetch origin 3b49e9de27e94f7ca041c8cf314e2b17d2732f80:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ocaml-bos
 * [new ref]         3b49e9de27e94f7ca041c8cf314e2b17d2732f80 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3b49e9d Bump and rebuild