Function push 

fn push(
    api: &Api<'_>,
    list: &str,
    dir: &Path,
    state: &mut State,
    state_path: &Path,
    zone: &TimeZone,
    report: &mut Report,
) -> Result<(), SyncError>

What changed here, sent: deleted, changed (patched, moved under its parent), new (inserted, parents first: Google has one level of steps). The state follows each answer, and is kept after each task made on Google.