$ git clone -n https://src.fedoraproject.org/rpms/rdiff-backup.git /var/lib/mock/f41-build-side-1-2768922-32100/root/chroot_tmpdir/scmroot/rdiff-backup
Cloning into '/var/lib/mock/f41-build-side-1-2768922-32100/root/chroot_tmpdir/scmroot/rdiff-backup'...
$ git fetch origin cb4f4ab90a0163802f5ad02d932c50f3a8d1407e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rdiff-backup
 * [new ref]         cb4f4ab90a0163802f5ad02d932c50f3a8d1407e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at cb4f4ab Remove old unused patches