Version comparison is naive

[scop]

gup version**

v0.27.1

Description (About the problem)

gup's version comparison is using a simple lexicographic string comparison. This does not work properly e.g. when the number of digits in a version changes.

Steps to reproduce

Example case added in #159 -- 1.2.0 is treated as newer than 1.11.5.

Expected behavior

1.2.0 is older than 1.11.5.

Additional details**

I don't know if the version comparison implementation used by go mod is exposed somewhere. But that would be a good one to use for this.

[nao1215]

@scop
Thank you for your contributions.
I believe that using the following library could resolve this bug in many cases.
https://github.com/hashicorp/go-version

I can create a new PR and fix it myself.
However, I think it would be better for you to update PR #159 so that your contribution record remains. What do you think?

[scop]

Thanks for addressing this! And no problem at all with not taking #159.

I had a look at that go-version lib myself, but seeing that it is documented to take semver and for example go module snapshot version numbers not following semver, I wasn't quite sure if it's the best choice. But I'm sure it will work fine for the majority of cases.

I would however suggest adding some snapshot versions to the test suite (e.g. grabbed with gup update -m something) to verify that it indeed works as intended for those versions as well.