Function parse 

pub fn parse(commit: &str, subject: &str, body: &str) -> Change

One commit, as a change.

The grammar is commit::Header’s, not a second one: the changelog and the commit validator read the same parse and disagree only about what to do with a header that is not conventional. Here that is not a failure — a commit nobody spelled conventionally still happened, and a changelog that dropped it would lie about what the release contains.