$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v9.0-u-ydi1-11282-29624/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v9.0-u-ydi1-11282-29624/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 2f788313d093a7c55742f2af69902fe74ed1f8d0:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         2f788313d093a7c55742f2af69902fe74ed1f8d0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 2f78831 bump release for test build