Function both_ways 

fn both_ways(
    client: &Client,
    dir: &Path,
    listed: &Listed,
    state: &mut State,
    state_path: &Path,
    report: &mut Report,
) -> Result<(), SyncError>

What changed here, sent; then, unless nothing changed on either side, what changed there, brought. The ctag is kept once both went through; what the server refused of an item is said once the rest is done.