$ git clone -n https://github.com/xcp-ng-rpms/xen /var/lib/mock/v8.3-u-tae1-10208-28783/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-tae1-10208-28783/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin af61b0c51818e87fdb66ad4a1d24b7d3ce749e17:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         af61b0c51818e87fdb66ad4a1d24b7d3ce749e17 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at af61b0c bump release for test build