$ git clone -n https://src.fedoraproject.org/rpms/hydra.git /var/lib/mock/f42-build-3532541-46326/root/chroot_tmpdir/scmroot/hydra
Cloning into '/var/lib/mock/f42-build-3532541-46326/root/chroot_tmpdir/scmroot/hydra'...
$ git fetch origin cd0bfc57eac506557a43d815827c70a8aaea502c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/hydra
 * [new ref]         cd0bfc57eac506557a43d815827c70a8aaea502c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cd0bfc5 cosmetics