Proposed changes

This makes some follow up adjustments to the PHP linting workflow after #176.

The linting workflow currently tries to pass the list of edited files to the phpcs command. This is causing an issue because the list of files output by the earlier step is a space separated list with each file surrounded in single quotes. Enclosing the list in double quotes to guard against possible security vulnerabilities is making phpcs read it as one file name.

The step responsible for generating a list of modified files is also configured incorrectly causing all modified files to be passed resulting in the workflow always running. Because path filtering is being used at the workflow level for the push events, this third party action is not required (it has actually been archived and abandoned upstream).

If a pull request is required to make a change to the code base, It's reasonable to assume that the branch was free of violations prior to creation. Because of this, it's fine to run the scan on the whole project. However, there are a few modifications that can also be made for performance and effectiveness:

• The The phpcs.xml file has been updated to accurately reflect the PHP and WordPress versions supported through the testVersion and minimum_supported_wp_version configuration settings, respectively.
• By default, running phpcs will now scan all PHP files in the repository except those explicitly excluded through an <exclude-patter> in the phpcs.xml file (which have been expanded to avoid scanning the vendor and node_modules directories).
• Caching between phpcs runs has been configured locally.
• When run within GitHub Actions, the results of the scan will be cached using actions/cache. The cache is keyed by the hash of the composer.lock and phpcs.xml files which control the behavior of phpcs, but an additional date value is included to ensure the cache is flushed at least once a week if those files don't change.
• Configuring Composer and installing dependencies is now handled by ramsey/composer-install, which handles caching and composer validate under the hood. Previously, there were unique steps in the linting workflow for this.
• Path filtering for push and pull_request events has been expanded to also include files that may affect the results of phpcs.
• Both path filtering and technote-space/get-diff-action are not required. The former has been archived, so removing this dependency is desired.
• Errors produced by a phpcs scan are now displayed contextually as annotations within pull requests and commits.
• Several warnings flagging unused variables have been addressed.

Type of Change

Production

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update
• Refactoring / housekeeping (changes to files not directly related to functionality)

Development

• Tests
• Dependency update
• Environment update / refactoring
• Documentation Update

Visual

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments