fix: show full option descriptions in --help output

[lovasoa]

Option descriptions in --help output were truncated to the first line. For example, npm version --help showed:

$ npm version --help
  --allow-same-version
    Prevents throwing an error when `npm version` is used to set the new

instead of the complete text:

$ npm version --help
  --allow-same-version
    Prevents throwing an error when `npm version` is used to set the new
    version to the same value as the current version.

This affected all commands, not just version.

Cause: getUsage() in lib/base-cmd.js used .split(n)[0] on each description, discarding everything after the first newline. Since descriptions are multi-line template literals, this cut most of them off mid-sentence.

Fix: Join all lines of the description into a single string instead of taking only the first line.

[owlstronaut]

Okay, I think this was actually an intentional design decision. Some of those descriptions are very long and --help is meant to give you a quick summary - i don't think we want full descriptions in there anyway. npm help version would give you the full text if that is what you wanted, i don't think showing everything here is the answer.

[lovasoa]

Sentences are cut in the middle without any explanation. Maybe the output should at least let the use know why and how to get the full description ?