add {before/after}_help_{short/long} to App struct

[jeffka11]

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• Searched the discussions
• Searched the closed issues

Describe your use case

I'm looking to use the help menu to replace creating a separate man page. To not bombard users with info, I'd like to include detailed information when they use the long --help flag for sections that need more detail. As a random example of more detail, if you "man curl", you'll see sections at the end explaining error codes that you wouldn't see with "curl --help" and I think {before/after}help{short/long} would provide that location.

Describe the solution you'd like

let myapp = App::new("My App")
    .after_help("footer message")  // this already exists
    .before_help("header message")  // this already exists

    .after_help_short("a concise footer")  // proposal, could be redundant with after_help
    .after_help_long("a much longer footer")  // proposal
    .before_help_short("a short header")  // proposal, could be redundant with before_help
    .before_help_long("a verbose header")  // proposal

Alternatives, if applicable

make man pages or a hook into cargo doc from clap, although I think the suggested solution is easier.

[kbknapp]

I think this would be implemented as {after,before}_help_long and allow the current {before,after}_help serve as the short so that we don't have redundant APIs. This also would go along with the short somewhat being the default in clap as with all other settings that where both a long and short co-exist.