pub fn ratio(old: &str, new: &str) -> f32 {
let old = super::lines::code_line_set(old);
let new = super::lines::code_line_set(new);
let base = old.len().min(new.len());
if base == 0 {
return 0.0;
}
let common = old.intersection(&new).count();
common as f32 / base as f32
}