$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-abourgeois1-9578-28328/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-abourgeois1-9578-28328/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin 21e5d161eb672aefa2da9653db0f46d9318f00ae:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         21e5d161eb672aefa2da9653db0f46d9318f00ae -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 21e5d16 bump release for test build