Function scan 

pub fn scan(root: &Path, paths: &[PathBuf], rules: &Rules) -> RepoStats

Count every path under root, grouped by language and ordered by code lines. Reads each file once; a path that is binary, oversized or unreadable is counted as skipped and never parsed.

What rules calls generated is left out, lockfiles included, the way a repository page counts: a lockfile runs to thousands of lines and would outrank the code beside it.