Function store 

fn store(
    dir: &Path,
    kind: Kind,
    state: &mut State,
    url: &str,
    (href, etag, data): (&str, &str, &str),
    report: &mut Report,
) -> Result<(), SyncError>

Writes an item brought from the server (href, ETag, text). Your version, changed here since the server last agreed on it (or never agreed), is set aside first, unless it is the same.