$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.3-u-prebuild-9332-28077/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-prebuild-9332-28077/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 7eaded399a61d2250b7da6db860b8d0418275d48:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         7eaded399a61d2250b7da6db860b8d0418275d48 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7eaded3 bump release for test build