Like was said in #2435, this is what people would expect.
While we should note this in a compatibility section in the changelog, I
do not consider this a breaking change since we should be free to adjust
the help output as needed. We are cautious when people might build up
their own content around it (like #3312) but apps should already handle
this with `--help` so this shouldn't be a major change.
We aren't offering a way for people to disable this, assuming people
won't need to. Longer term, we are looking at support "Actions" (#3405)
and expect those to help customize the flags. We'll need something
similar for the `help` subcommand.
Fixes#3440
Adding in a `StructOpt` derive with `structopt` attributes, with
deprecation notices. Unofrtunately, not as many deprecation warnings as
I would like. Apparently, you can't do them for a `use` of a derive? I
also wanted to inject code that would trigger a deprecation notice for
attributes but that would require enough of a refactor that I didn't
consider it worth it. We are at least providing a transition window
even if it means we'll have to remvoe it next major release without a
deprecation warning.
