$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v9.0-u-ydi1-11090-29520/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v9.0-u-ydi1-11090-29520/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin c17daf3dbc812fa7f3b23b15fedbafd8cfa3c0ab:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         c17daf3dbc812fa7f3b23b15fedbafd8cfa3c0ab -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c17daf3 bump release for test build