$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v9.0-u-ydi1-11584-29879/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v9.0-u-ydi1-11584-29879/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 65658291bb780550074d64ae99d7d6b16c0e4b68:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         65658291bb780550074d64ae99d7d6b16c0e4b68 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6565829 bump release for test build