$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v9.0-u-ydi1-11381-29683/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v9.0-u-ydi1-11381-29683/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin b239189922ae20415da634e2212e36bc2930ab19:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         b239189922ae20415da634e2212e36bc2930ab19 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b239189 bump release for test build