$ git clone -n https://src.fedoraproject.org/rpms/systemd.git /var/lib/mock/f40-build-1512074-23908/root/chroot_tmpdir/scmroot/systemd
Cloning into '/var/lib/mock/f40-build-1512074-23908/root/chroot_tmpdir/scmroot/systemd'...
$ git fetch origin 948fb506e4e46519a0397afe19d89660c52c98d3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/systemd
 * [new ref]         948fb506e4e46519a0397afe19d89660c52c98d3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 948fb50 Version 255.8