Function path_gitattribute_value 

pub fn path_gitattribute_value(
    rules: &[AttrRule],
    path: &str,
    is_dir: bool,
    attr_name: &str,
) -> Option<String>

Return the final value assigned to attr_name for path.

rules is the ordered set of parsed attribute rules, path is repository-relative, is_dir selects directory-only pattern handling, and attr_name is the attribute to query.

Returns "set", "unset", or an explicit string value. None means the attribute is unspecified after all matching rules are applied.