Function diff_paths 

pub fn diff_paths(
    a: &Path,
    b: &Path,
    opts: &DiffOptions,
) -> Result<Vec<FileDiff>, NoIndexError>

Diff two filesystem paths (files, directories, or one of each).

Does not require a Repository. Directory pairs are walked recursively with sorted names; a file paired with a directory compares against directory/basename(file) like Git. Symlink targets are diffed as text; executable bit differences appear as mode changes.

Errors

Returns NoIndexError::PathNotAccessible when either top-level path cannot be accessed.