$ git clone -n https://src.fedoraproject.org/rpms/systemd.git /var/lib/mock/f40-build-1942260-25164/root/chroot_tmpdir/scmroot/systemd
Cloning into '/var/lib/mock/f40-build-1942260-25164/root/chroot_tmpdir/scmroot/systemd'...
$ git fetch origin f6ffb69dde4ef42eaabfa1488716f65118d7e569:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/systemd
 * [new ref]         f6ffb69dde4ef42eaabfa1488716f65118d7e569 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f6ffb69 Fix release field