Function diff 

pub fn diff(
    source: Option<Utf8PathBuf>,
    icons_override: Option<IconsMode>,
    no_color: bool,
) -> Result<()>

yui diff [--icons MODE] [--no-color] — for every drifted entry (link or render), print a unified diff to stdout.

Layered on top of the same drift detection yui status uses (absorb::classify + render dry-run), but actually emits the content delta. InSync / Restore / RelinkOnly entries are suppressed — they’re not “drift the user can read”.