$ git clone -n https://src.fedoraproject.org/rpms/R-unitizer.git /var/lib/mock/f42-build-side-110318-58926843-6569309/root/chroot_tmpdir/scmroot/R-unitizer
Cloning into '/var/lib/mock/f42-build-side-110318-58926843-6569309/root/chroot_tmpdir/scmroot/R-unitizer'...
$ git fetch origin bb3e444269a4d20b3a8c28546ee65a8d0b395607:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-unitizer
 * [new ref]         bb3e444269a4d20b3a8c28546ee65a8d0b395607 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bb3e444 Update to latest version