Fix PHPcs baseline test failure when there are no files to check

[Tjitse-E]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/mage-os/github-actions/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Currently the PHPCS baseline tests are failing when there are no files to check. See https://github.com/mage-os/mageos-magento2/actions/runs/5794755408/job/15940229468?pr=32.

What is the new behavior?

• Stop before composer install step when phpcs has no files to check
• Only run phpcs for files in the app dir
• Simplify action, by utilising the build in function of tj-actions/changed-files to check which files were modified.
• Trigger error when phpcs baseline was not created.
• Run phpcs on all filetypes that are specified in the Magento ruleset

Does this PR introduce a breaking change?

• Yes
• No

Additional information

• Example run with adding an additional error in app/code/Magento/Catalog/view/frontend/templates/product/breadcrumbs.phtml, while there are existing errors in breadcrumbs.phtml (that are now in the baseline, so shoudn't be reported).
• Example run when there are no relevant phpcs files changed.

Related PR

mage-os/mageos-magento2#32

[Tjitse-E]

@Vinai i've resolved the issue that occured last friday (the baseline test didn't work on forked repo's). We now have a successfull run: https://github.com/mage-os/mageos-magento2/actions/runs/6149981258/job/16686980485?pr=34.

[Vinai]

Thank you, I will review!
Can you join us today at 3pm CET for the weekly tech meeting by chance?
It's in the voice channel on Discord.

[Vinai]

LGTM, thank you!