ci: add eslint check to only check changed files and fail when warnings are thrown

[kieckhafer]

Impact: minor
Type: ci|performance

Issue

We currently have ~300 eslint warnings related to jsdoc.

Solution

To incrementally fix all these issues. we will add a check to the CI process to throw an error if there are any eslint errors OR warnings, only files you changed in your PR. In addition to only checking changed files, this is different than our traditional eslint CI check in that it will not pass even if there are warnings, where our traditional check only fails against errors.

Breaking changes

None

Testing

1. Make any change (add a random comment in the file somewhere) to multiples file that is currently throwing an eslint warning, and make a PR with said change. Two files with eslint warnings:

• • imports/plugins/included/product-variant/client/templates/products/productSettings/productSettings.js
• • client/modules/core/main.js

1. see that CI does not pass until warnings is fixed

I made a few test commits with purposefully failing files, you can see the CI check running and failing when there are eslint warnings (not errors): https://circleci.com/gh/reactioncommerce/reaction/49620?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-checks-link

[kieckhafer]

@mikemurray could you please see that this works as it should, since you know what it's supposed to do?

@aldeed / @focusaurus could you please check the bash script / config file code?

[focusaurus]

I pushed a commit to refactor the bash script a bit. You'll need to re-test nothing broke but I'm fairly confident it will still work properly. Otherwise looks good.

[kieckhafer]

@mikemurray confirmed @focusaurus's changes still work.

Here is the latest CI run that is failing on purpose, should be good enough for testing: https://circleci.com/gh/reactioncommerce/reaction/49757?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-checks-link