$ git clone -n https://github.com/xcp-ng-rpms/expat /var/lib/mock/v8.3-incoming-9188-27993/root/chroot_tmpdir/scmroot/expat
Cloning into '/var/lib/mock/v8.3-incoming-9188-27993/root/chroot_tmpdir/scmroot/expat'...
$ git fetch origin 8d6743a03748fe3225de12fb53592e3c84b6938a:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/expat
 * [new ref]         8d6743a03748fe3225de12fb53592e3c84b6938a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8d6743a Merge pull request #3 from xcp-ng-rpms/8.3-XS-1523