$ git clone -n https://src.fedoraproject.org/rpms/catfish.git /var/lib/mock/f39-build-1557597-37298/root/chroot_tmpdir/scmroot/catfish
Cloning into '/var/lib/mock/f39-build-1557597-37298/root/chroot_tmpdir/scmroot/catfish'...
$ git fetch origin b3873f7de0db3c93dc2c6667a90fb8302b8499ba:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/catfish
 * [new ref]         b3873f7de0db3c93dc2c6667a90fb8302b8499ba -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b3873f7 4.18.0