Support opening a web page for extensive help

Issue #400 asks for allowing users to write examples, but I think that might be asking too much of what's available from the command line. It's nice to have all your help in one spot, but practically speaking, it adds some baggage. For example, if all the documentation is compiled into the project itself, if somebody wants to contribute better help, it has be be pull-requested into the project, built, released and deployed. That's not to mention that command windows aren't really optimized for presenting multiple pages of text.

There are several systems that support a different model, where there's a way to bring up a web page from the command line. Let's take a familiar example: 'git checkout --help' brings up extensive help for checkout in your web browser. As the git example shows, it's a popular idea, but there's not a clearly preferred way to do it: 'git' actually implements this idea in two ways because there's also 'git help checkout' which is the same as 'git checkout --help'. Given this, it'll surprise noone that 'git help checkout' takes you to a web page but 'git help' does not.

So if there's a clear and consistent way to implement this thing, git hasn't discovered it. Perhaps somebody else can point to a more successful example?

For our team, we're fond of the name '--wiki' because that's where we house our documentation. Our reasoning is simply that our tools are released to a limited audience, so we're happy to have anybody contribute back better help and have it get shared immediately, rather than having to wait for a release cycle to bring forth the goodness.

Thoughts?

Beginne mit der Überprüfung der vorhandenen Einstiegspunkte für die Befehlszeilenhilfe und vergleiche das Verhalten von `git checkout --help` und `git help checkout`. Lege eine konsistente Option wie `--wiki` fest, einschließlich der Zuordnung zur Web-Dokumentation und dessen, was für den grundlegenden `git help`-ähnlichen Befehl geschehen soll.

Vom Indexierungsmodell aus dem Issue-Text verfasst.