$ git clone -n https://src.fedoraproject.org/rpms/python-cython0.29.git /var/lib/mock/f40-build-2634271-65994/root/chroot_tmpdir/scmroot/python-cython0.29
Cloning into '/var/lib/mock/f40-build-2634271-65994/root/chroot_tmpdir/scmroot/python-cython0.29'...
$ git fetch origin 16446b50e20789356b82add2b7defb3b83feeb0f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/python-cython0.29
 * [new ref]         16446b50e20789356b82add2b7defb3b83feeb0f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 16446b5 Retired, see https://bugzilla.redhat.com/2254029