Only run phpcs on changed files

[andybroomfield]

Possible action here https://github.com/marketplace/actions/action-phpcs

To avoid need for sudden rule changes to require mass update and releases of modules.

[millnut]

I can see the benefit here for only checking changed files, however, we could end up moving technical debt around coding standard changes to a non-visible location at a module level (the project will still check all code).

This would then mean it's the module maintainer's responsibility to manually check all their code against coding standards or have an automated workflow daily/weekly to run the coding standards check against all code.

An alternative is we have two coding standards checks one which only checks changed files for use in PRs and the existing one which would be used for anything else e.g. manual workflow runs.

I believe drupal.org pipeline/workflow checks everything and not just changed files.