$ git clone -n https://github.com/xcp-ng-rpms/xen.git /var/lib/mock/v8.3-u-stormi1-8825-27767/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-stormi1-8825-27767/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 556ba8f0ebe3d1889cbfd3a0db0a8eecc701932e:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         556ba8f0ebe3d1889cbfd3a0db0a8eecc701932e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 556ba8f bump release for test build