Function classify 

pub fn classify(change: &Change, old: &Package, new: &Package) -> Verdict

Classifies one change against the two snapshots it was drawn from.

old and new are the matched packages the change belongs to; the change’s path is resolved against them to recover the typed IR the direction is read from. For a package present on only one side the caller passes that package as both arguments — those changes classify on their category alone.