Function unified_diff 

pub fn unified_diff(
    old_content: &str,
    new_content: &str,
    old_path: &str,
    new_path: &str,
    context_lines: usize,
    indent_heuristic: bool,
    quote_path_fully: bool,
) -> String

Unified diff for two text sides with default a/ / b/ path prefixes.