$ git clone -n https://src.fedoraproject.org/rpms/ghc-system-fileio.git /var/lib/mock/f40-build-2055575-49119/root/chroot_tmpdir/scmroot/ghc-system-fileio
Cloning into '/var/lib/mock/f40-build-2055575-49119/root/chroot_tmpdir/scmroot/ghc-system-fileio'...
$ git fetch origin cbb26954c594a117007d8ecdd2a3f76bb00dbca5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ghc-system-fileio
 * [new ref]         cbb26954c594a117007d8ecdd2a3f76bb00dbca5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cbb2695 bump release