Function diff_forced_binary_by_driver 

pub fn diff_forced_binary_by_driver(
    git_dir: &Path,
    config: &ConfigSet,
    path: &str,
    old_mode: &str,
    new_mode: &str,
) -> bool

Force Binary files ... differ when the path’s diff driver sets binary, except for symlinks.

Matches Git’s diff_filespec_is_binary driver flag: diff.<name>.binary applies to paths using that driver, but symlink modes (120000) still emit textual symlink-target patches (t4011).