$ git clone -n https://github.com/xcp-ng-rpms/guest-templates-json.git /var/lib/mock/v8.3-incoming-9973-28628/root/chroot_tmpdir/scmroot/guest-templates-json
Cloning into '/var/lib/mock/v8.3-incoming-9973-28628/root/chroot_tmpdir/scmroot/guest-templates-json'...
$ git fetch origin ef9e5bba67842ab179355b0d732115e8a956a7f7:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/guest-templates-json
 * [new ref]         ef9e5bba67842ab179355b0d732115e8a956a7f7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ef9e5bb Merge pull request #16 from xcp-ng-rpms/8.3-rebase-XS-2.0.15-1