Implement path-filtered CI triggers in a monorepo with GitHub Actions

Steps

1. Use native path filters on push and pull_request events to trigger a workflow only when relevant files change: on: { push: { paths: ['services/api/**', 'shared/**'] } }
2. Add paths-ignore at the workflow level to exclude documentation or config files that should not trigger builds: paths-ignore: ['docs/**', '**.md']
3. For fine-grained per-job filtering inside a single workflow, use the dorny/paths-filter action: it outputs boolean variables per defined path pattern that you can reference in subsequent job conditions via if: needs.changes.outputs.api == 'true'
4. Always include the workflow file itself in path filters (e.g., .github/workflows/api.yml) so that CI configuration changes are validated without requiring a source code change
5. Include shared library paths in every service's path filter; if service A depends on shared/utils/, changes there should trigger service A's CI even if no service A files changed
6. Be aware that paths filters on pull_request do not apply when the PR is added to a merge queue — merge_group events ignore path filters and always run the workflow