$ git clone -n https://src.fedoraproject.org/rpms/fbrnch.git /var/lib/mock/f38-build-side-42-init-devel-1026154-29689/root/chroot_tmpdir/scmroot/fbrnch
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1026154-29689/root/chroot_tmpdir/scmroot/fbrnch'...
$ git fetch origin 3bbf4c9cc194fdec58b5fe0bac2c810dca8735d5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/fbrnch
 * [new ref]         3bbf4c9cc194fdec58b5fe0bac2c810dca8735d5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3bbf4c9 refresh to cabal-rpm-2.1.0