$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-gtn1-8885-27840/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-gtn1-8885-27840/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin 3b1b3321890dcda046c89510e1daa087f00a4092:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         3b1b3321890dcda046c89510e1daa087f00a4092 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3b1b332 bump release for test build