$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v9.0-u-ydi1-11091-29520/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v9.0-u-ydi1-11091-29520/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 0670e39609aeb136600201b54eb97dbe7258778f:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         0670e39609aeb136600201b54eb97dbe7258778f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0670e39 bump release for test build