Acceptance+handling of partial versions in - ranges not documented

[cvrebert]

The only example of the - range operator in the README shows it being used with full versions, but some testcases have it also being used with incomplete versions, in particular with novel handling of incomplete upper-bounds: https://github.com/isaacs/node-semver/blob/v2.2.1/test/index.js#L491
This should be documented.

It's funny, the things you run into when trying to write a clean-room implementation...

[isaacs]

So... on this one, I'm a bit torn.

I added the tests because I wanted to at least know if the behavior ever changes, just in case it would break anyone.

But, I'm tempted to say that a X.Y - A.B.C range should maybe be an error? At least, that's why it wasn't documented in the first place.

Out of curiosity, are you writing a clean-room implementation of this for? I've been meaning to document the range syntax as a proper specification eventually, maybe this could be a good justification for doing that, along with a comprehensive suite of tests etc.

[cvrebert]

But, I'm tempted to say that a X.Y - A.B.C range should maybe be an error?

Your call obviously. I basically just care about the syntax+semantics getting adequately doc'd/spec'd, regardless of what exactly the spec'd syntax+semantics are.

Out of curiosity, [what] are you writing a clean-room implementation of this for?

I'm writing a Python library that parses various ecosystems' dependency specifications (e.g. package.json, requirements.txt, pom.xml), which shall include understanding the version compatibility constraints, and I'm trying to support npm as one of the ecosystems.

[isaacs]

Fixed on v4, #99