Add stylelint to pre-commit hook

[brianbancroft]

The following is a basic implementation of StyleLint on the pre-commit hook. It's not quite ready for prime-time as I have two areas I still haven't figured out:

• Testing. I'm still stuck on how to test it
• Unexpected output error (see screencap 1) (regex. Still looking at it)

Screencaps

Bad CSS

Below in another repo, I added the gem locally, and added some gobbedly-gook in the CSS. This is the output:

Good CSS

Here's what it looks like otherwise:

Closes #514 if resolved

[sds]

Thanks for the pull request, @brianbancroft.

Overall this looks fine, but as you mentioned it's missing tests. Good tests for hooks simply ensure that the branches of the hook's logic are executed. In your case, you want to check what happens when:

• The stylelint command returns a zero exit status
• The stylelint command returns a non-zero exit status
• The stylelint command prints messages (i.e. is your regex working and correctly attributing file name and line number?)

See https://github.com/brigade/overcommit/blob/master/spec/overcommit/hook/pre_commit/scss_lint_spec.rb for an example. Happy to merge once tests are in place. Thanks!

[sds]

Let's leave this out for now. We'll update the version when we release the next version. Thanks!

[sds]

Finished in #590