$ git clone -n https://github.com/xcp-ng-rpms/xapi.git /var/lib/mock/v8.3-u-gtn1-10254-28829/root/chroot_tmpdir/scmroot/xapi
Cloning into '/var/lib/mock/v8.3-u-gtn1-10254-28829/root/chroot_tmpdir/scmroot/xapi'...
$ git fetch origin 5142f849d62288d8e4426aa40c38b000a4d05e53:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/xapi
 * [new ref]         5142f849d62288d8e4426aa40c38b000a4d05e53 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5142f84 bump release for test build