Only run GitHub Actions if certain files were changed

[DavidoTek]

Currently, the tests are run for every push to a PR branch. Only run tests for changed files:

• Only run AppSteam Metainfo Valdation if the metainfo XML file was changed
• Only run PyTest if a .py file was changed

---

https://stackoverflow.com/a/63822945 :

on:
  push:
    paths:
      - folder1/**

[sonic2kk]

The on/push/paths only works on a per-Workflow level. The way our tests are set up, we have one Workflow testing-ci.yml which has two jobs: "Run PyTest" and "Run AppStream Metainfo Validation".

If we absolutely want to keep these in the same CI, we can look into the changed-files action. I'm not sure how to use it from browsing the docs, it isn't clear to me how we specify "if files in X folder changed".

If we split the PyTest suite and AppStream Metainfo Validation these out into separate Workflows, then we cna use the on/push/paths YML block :-)

Side note: Either way, we may want to rename the name of our testing-ci.yml. The filename is fine, but the Workflow title itself is "Test using Pytest" which is not wholly accurate when it also runs the AppStream Metainfo stuff. Having said that, I don't have a better name in mind at time of writing 😅