$ git clone -n https://src.fedoraproject.org/rpms/ghc-boxes.git /var/lib/mock/f40-build-2085791-50093/root/chroot_tmpdir/scmroot/ghc-boxes
Cloning into '/var/lib/mock/f40-build-2085791-50093/root/chroot_tmpdir/scmroot/ghc-boxes'...
$ git fetch origin bc3df4866565b919cebf33f05681bd27cea9fe9a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-boxes
 * [new ref]         bc3df4866565b919cebf33f05681bd27cea9fe9a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bc3df48 bump release