$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.2-u-tescande1-8874-27831/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.2-u-tescande1-8874-27831/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin ff0d3faf921fc60efc6d68437af710e6adecee23:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         ff0d3faf921fc60efc6d68437af710e6adecee23 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ff0d3fa bump release for test build