Show HN: Header-only, extensible C++17 argument parser

I agree with you, but a user can easily wrap their own to avoid the boilerplate for adding arguments. An example would be:

  // Could provide more detailed usage if wanted.
  constexpr char USAGE[] = "./program --input_path input --output_path output";
  int main(int argc, char** argv) {
    const flags::args args(argc, argv);
    const auto input_path = args.get<std::string>("input_path");
    const auto output_path = args.get<std::string>("output_path");

    if (!input_path || !output_path) {
      std::cerr << USAGE << std::endl;
      return 1;
    }

    std::cout << "success: " << *input_path << " to " << *output_path
              << std::endl;
    return 0;
  }

The primary goal of this is to be simple to use and implement in your project, but I can see the use of a simple validation function which provides the same functionality as the above.