$ git clone -n https://github.com/xcp-ng-rpms/xs-opam-repo.git /var/lib/mock/v8.3-incoming-9785-28499/root/chroot_tmpdir/scmroot/xs-opam-repo
Cloning into '/var/lib/mock/v8.3-incoming-9785-28499/root/chroot_tmpdir/scmroot/xs-opam-repo'...
$ git fetch origin ae42847ed34a9c711e55985dd2685d26b8f4950a:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xs-opam-repo
 * [new ref]         ae42847ed34a9c711e55985dd2685d26b8f4950a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ae42847 Import xs-opam-repo-6.96.0-1.xs8.src.rpm (#12)