$ git clone -n https://src.fedoraproject.org/rpms/polymake.git /var/lib/mock/f40-build-1844912-24972/root/chroot_tmpdir/scmroot/polymake
Cloning into '/var/lib/mock/f40-build-1844912-24972/root/chroot_tmpdir/scmroot/polymake'...
$ git fetch origin a6e769d0c1ce47d3a9d6464f2230bfa63a26a515:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/polymake
 * [new ref]         a6e769d0c1ce47d3a9d6464f2230bfa63a26a515 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a6e769d Version 4.12