$ git clone -n https://src.fedoraproject.org/rpms/ghc-constraints.git /var/lib/mock/f38-build-side-42-init-devel-701812-27072/root/chroot_tmpdir/scmroot/ghc-constraints
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-701812-27072/root/chroot_tmpdir/scmroot/ghc-constraints'...
$ git fetch origin 3bf984dcfebda84f932a13feff382dfe87d94a01:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-constraints
 * [new ref]         3bf984dcfebda84f932a13feff382dfe87d94a01 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3bf984d Added the README