Add command line capability to print out the full docstring of a session

[namurphy]

How would this feature be useful?

When I'm writing a noxfile.py, I sometimes write helpful or contextual information in a second paragraph in the docstring of a session (such as in this session).

Individual session docstrings can be used to:

• Show examples of how to invoke a nox session
• Describe the different parametrizations of a session
• Describe arguments that are often passed to a session (e.g., a filename or a pytest flag to run only certain tests)
• Describe differences for when a session is invoked locally vs. in CI

Describe the solution you'd like

Currently, doing nox -l print outs only the first lines of docstrings, but I don't know of a way to print out the full docstrings.

Some possible syntaxes would be:

1. nox -l session_name to print out the full docstring of a session
2. nox -l -v to print out the full docstrings of all the sessions (though this would get lengthy)

Describe alternatives you've considered

• Create a new command line flag, like nox -d session_name (which would keep things separate, but it may be harder to remember)
• Include contextual information in the top-level docstring of noxfile.py (which would become unwieldy for a large noxfile.py)

Anything else?

Thank you so much to everyone who created this wonderful tool!

[DiddiLeija]

I guess we can add this (indeed, could be very helpful), as long as we don't mess up with the syntax and make it complicated 😅

I'd go for the first suggested syntax (though I'd like to see what other maintainers think tbh)