What's the proper way to use std.getopt?

[Jordi Gutiérrez Hermoso]

I don't quite understand what to do if getopt throws. I would 
have hoped for something like

    int arg1;
    string arg2;
    auto parser = getopt("opt1", "docstring 1", &arg1, "opt2", 
"docstring 2", &arg2);
    try {
      auto opts = parser.parse(args)
    }
    except(BadArguments) {
      parser.showHelpString();
    }

but instead, the docstring from getopt is only generated if all 
arguments are valid, i.e. when it's the least needed because the 
user already knew what to input.

What's the proper style, then? Can someone show me a good example 
of how to use getopt and the docstring it automatically generates?