Function get_user_file_ownership 

pub fn get_user_file_ownership(
    username: &str,
    by_email: bool,
    top: usize,
    sort_pct: bool,
) -> Result<Vec<(String, usize, usize, f32)>, String>

Compute per-file ownership for a user.

• username: match against blame author (by_name) or author-mail (by_email)
• by_email: if true, compare normalized emails; otherwise compare author name
• top: max rows to return (use usize::MAX to disable)
• sort_pct: if true, sort by percentage desc; otherwise by user_loc desc