Function aggregate_reviews 

pub fn aggregate_reviews<'a>(
    metas: impl IntoIterator<Item = &'a CommitMeta>,
    email: bool,
) -> Vec<Review>

Count, per reviewer, the commits they signed off on via Acked-by / Tested-by / Reviewed-by trailers. A reviewer is credited at most once per commit even if they appear in several of those trailers. Returned in descending commit count, ties broken by first-seen order.