Function short_help 

pub fn short_help(
    spec: &Spec<'_>,
    path: &[&str],
    chain: &[&CommandMeta<'_>],
) -> String

Everything -h prints.

The short form: one line per entry, its help beside it. --help renders the same content through a wider layout, which is the next thing to build — the two differ in presentation and in which help text they prefer, not in what they cover.

path is the command as invoked, as for usage_line.