Document Command class in readme

[nicojs]

I've noticed that by using the documented const program = require('command') syntax you're actually polluting a global Command object. This can be shared by other components resulting in weird issues (like nicojs/node-link-parent-bin#4 (comment))

After inspecting the source code, i see that a Command class is exported! Kudo's to you sir! I'll use this from now on. It also helps quite a bit with testability (injecting a mock object for Command at test time). Let's promote this way of working a bit by documenting it in the readme

My idea is to update the readme and use const Command = require('commander').Command; const program = new Command(); everywhere. I would like to place a remark to let people know that they could also use const program = require('commander'); but that it is not preferred and explain why it is not.

If you agree, I'm willing to create the PR.

I would personally like it if the const program = require('commander');-way-of-working would become deprecated and removed in a major release. What are your thoughts on that?

[shadowspawn]

We do need to get something into the README about the "new" pattern, thanks for raising.

I don't think we will deprecate the old way as such, but it should be the my-program-is-so-simple-globals-are-ok way of working.

[shadowspawn]

I have added the new pattern in a large update to README in #953

[nicojs]

Awesome! LGTM

[shadowspawn]

Updated README with section right at start showing use of Command class
https://github.com/tj/commander.js#declaring-program-variable