$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-gtn1-10246-28822/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-gtn1-10246-28822/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin d66710dcaa9b6255c878b9c0a9cc14e8f8bc8d13:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         d66710dcaa9b6255c878b9c0a9cc14e8f8bc8d13 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d66710d bump release for test build