$ git clone -n https://src.fedoraproject.org/rpms/mapnik.git /var/lib/mock/f41-build-815567-149590/root/chroot_tmpdir/scmroot/mapnik
Cloning into '/var/lib/mock/f41-build-815567-149590/root/chroot_tmpdir/scmroot/mapnik'...
$ git fetch origin b4e19fbea2bca77bea16dcd15ea8584f771860e1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mapnik
 * [new ref]         b4e19fbea2bca77bea16dcd15ea8584f771860e1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b4e19fb Update to 4.0.0 upstream release