CI: Run plugin tests only when code changes

[skoeva]

These changes extend ci.yml with a find_changed_plugins pre-job so only the plugins affected by a PR are tested, rather than running all three on every push.

Fixes: #594

Summary

• Adds a find_changed_plugin job that uses git diff origin/main...HEAD to dynamically build a matrix of only the plugins with changed files
• All jobs (test, lint, build, security) consume the dynamic matrix and are skipped entirely if no plugins changed
• translations job runs only when aks-desktop, ai-assistant, or Localize/ is touched
• If any file outside plugins/ or Localize/ changes (e.g. .github/, root package.json, shared scripts), all plugins run as a fallback
• Follows the same pattern used in headlamp-k8s/plugins

Testing

• Open a PR touching only plugins/aks-desktop and verify only aks-desktop jobs run
• Open a PR touching only plugins/ai-assistant and verify only ai-assistant jobs run
• Open a PR touching only plugins/insights-plugin and verify only insights-plugin jobs run
• Open a PR touching only Localize/** and verify only the translations job runs
• Open a PR touching a root-level file (e.g. package.json) and verify all plugins run

[illume]

Can be done keeping the one file?

I remember doing something like this in the plugins repo with one file. Hrmm.

[skoeva]

@illume I think so...I just thought it would be nice to split things up like in the main headlamp repo. I suppose one file would be good in the case that we add more plugins

[Copilot]

Pull request overview

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[Copilot]

Pull request overview

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[Copilot]

git diff --name-only origin/main...HEAD won’t correctly detect changes on push events to main (after the push, origin/main typically points at the same commit as HEAD, so the diff is empty and the workflow falls back to “run all plugins”). If the goal is to reduce work on both PRs and pushes (as described), consider selecting the diff base by event type (e.g., for push: ${{ github.event.before }}..${{ github.sha }}; for pull_request: ${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }}) instead of always using origin/main...HEAD.