$ git clone -n https://src.fedoraproject.org/rpms/ocaml-gsl.git /var/lib/mock/f40-build-768410-125306/root/chroot_tmpdir/scmroot/ocaml-gsl
Cloning into '/var/lib/mock/f40-build-768410-125306/root/chroot_tmpdir/scmroot/ocaml-gsl'...
$ git fetch origin f850755b21d731e317f45133a6f4339c77ffbd41:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ocaml-gsl
 * [new ref]         f850755b21d731e317f45133a6f4339c77ffbd41 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f850755 Bump release and rebuild