$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-gtn1-10304-28873/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-gtn1-10304-28873/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin c59c7a2f0511bd26cb1147f86a613d28e69ac0d6:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         c59c7a2f0511bd26cb1147f86a613d28e69ac0d6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c59c7a2 bump release for test build