$ git clone -n https://src.fedoraproject.org/rpms/luxcorerender.git /var/lib/mock/f39-build-1641974-40210/root/chroot_tmpdir/scmroot/luxcorerender
Cloning into '/var/lib/mock/f39-build-1641974-40210/root/chroot_tmpdir/scmroot/luxcorerender'...
$ git fetch origin 5b5990e2c799ce4919751ac2e7edaa16b99d4315:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/luxcorerender
 * [new ref]         5b5990e2c799ce4919751ac2e7edaa16b99d4315 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5b5990e Update to 2.7 beta1 (rhbz#2219126)