$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-gtn1-9529-28262/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-gtn1-9529-28262/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin 4195b05677c1e967a0bd0a28a67c93505911150b:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         4195b05677c1e967a0bd0a28a67c93505911150b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4195b05 bump release for test build