$ git clone -n https://src.fedoraproject.org/rpms/rpy.git /var/lib/mock/f39-build-1505449-35140/root/chroot_tmpdir/scmroot/rpy
Cloning into '/var/lib/mock/f39-build-1505449-35140/root/chroot_tmpdir/scmroot/rpy'...
$ git fetch origin 29bc9f5641ceb9726e98964030ca13164176e1ea:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rpy
 * [new ref]         29bc9f5641ceb9726e98964030ca13164176e1ea -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 29bc9f5 Update to 3.5.14