Function stat_changed 

pub fn stat_changed(
    b_size: u64,
    b_mtime: i64,
    b_nanos: Option<u32>,
    size: u64,
    mtime: i64,
    nanos: u32,
) -> bool

Whether a file’s stat differs from its baseline stamp. Size and seconds always; nanoseconds only when the baseline recorded them — a baseline written before nanoseconds were stamped has None, and comparing against a missing value would re-upload every file once.