$ git clone -n https://github.com/xcp-ng-rpms/xen /var/lib/mock/v8.3-u-tae2-9179-27989/root/chroot_tmpdir/scmroot/xen
Cloning into '/var/lib/mock/v8.3-u-tae2-9179-27989/root/chroot_tmpdir/scmroot/xen'...
$ git fetch origin 532d6041d2b7ef1c80a3f30b490ebb8ae5f02bc7:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xen
 * [new ref]         532d6041d2b7ef1c80a3f30b490ebb8ae5f02bc7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 532d604 bump release for test build