Problem

When use_rest_api: true is set, only pull_request* events are supported. For push, merge_group, and all other events, actions/checkout is required. For large repositories, the checkout step adds significant time to workflows that only need to know which files changed (e.g., conditional job triggers, path-based filtering).

This also creates a poor user experience for teams using merge queues. A workflow with use_rest_api: true works correctly on pull_request events, but then fails when the same workflow triggers on merge_group as the PR moves into the merge queue — or on push when it lands on the target branch. Users either have to add actions/checkout (losing the performance benefit) or maintain separate workflow configurations per event type.

Proposed solution

Extend the REST API mode to support push and merge_group events by using the repos.compareCommits endpoint instead of pulls.listFiles. The webhook payload already contains the necessary SHAs:

• push: payload.before / payload.after
• merge_group: payload.merge_group.base_sha / payload.merge_group.head_sha

Both endpoints return files in the same shape (filename, status, previous_filename), so all downstream processing (filtering, dir_names, output formatting, etc.) works without changes.

Prior art

This pattern is proven in the wild. Two maintained forks of jitterbit/get-changed-files use repos.compareCommits for API-only changed file detection across event types, with no checkout required:

• Ana06/get-changed-files (71 stars) — supports pull_request, pull_request_target, and push via API
• npwolf/get-changed-files — supports pull_request, pull_request_target, push, and merge_group via API

Scope

• getChangedFilesFromGithubAPI in changedFiles.ts — branch endpoint selection by event type
• Gate in main.ts — allow push/merge_group through to the REST API path
• Unit tests for both the API function and routing logic
• No changes to the git-based code path or any existing inputs/outputs

Limitations

The same 3,000-file cap that applies to pulls.listFiles also applies to repos.compareCommits. This is a GitHub API limitation, not specific to this implementation.