Option to display None default?

If it does not conflict with how argparse works, I think it would be useful to have an option that allows explicitly displaying when the developer has specified that an argument defaults to None internally if not provided. This is useful for arguments where the default case shares some, but not all, functionality with another case that may appear the same to the use but actually isn't. E.g., in my project None and 0 have very similar, but non-identical behavior, as None ensures the value is ignored, while 0 specifies to consider it, but treat it as 0, which doesn't do exactly the same thing.

Start by tracing how the extension renders argparse options and defaults, then compare that behavior with argparse's handling of explicitly specified None defaults. Define how an option should distinguish an explicit None from other defaults without conflicting with argparse, and verify the None-versus-0 example as the done criterion.