$ git clone -n https://src.fedoraproject.org/rpms/RBTools.git /var/lib/mock/f39-build-1646587-40409/root/chroot_tmpdir/scmroot/RBTools
Cloning into '/var/lib/mock/f39-build-1646587-40409/root/chroot_tmpdir/scmroot/RBTools'...
$ git fetch origin 7cd11b0c319e838a2d3c6c3f57a612f878459bb8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/RBTools
 * [new ref]         7cd11b0c319e838a2d3c6c3f57a612f878459bb8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7cd11b0 Update to 4.1