Adopt GitHub Copilot code review with custom instructions across Tekton repos

[vdemeester]

Background

As of December 2025, CNCF provides free GitHub Copilot Enterprise licenses to CNCF project maintainers. Now that Tekton is a CNCF project, we're eligible to take advantage of this — including Copilot code review, which analyzes pull requests to surface bugs, suggest improvements, and enforce consistency before a human reviewer looks at the diff.

This is a potential time-saver for our maintainers, who carry a heavy review load across pipeline, triggers, cli, dashboard, chains, and other repos.

Proposal

Evaluate and (if we agree) roll out Copilot code review across Tekton repositories, configured per-repo so each project can tune it to its own conventions.

GitHub gives us a few levers to control behavior per repository:

1. Custom instructions — .github/copilot-instructions.md (repo-wide) and path-specific .github/instructions/*.instructions.md files. Natural-language guidance applied to every review (e.g. Go conventions, Knative reconciler patterns, codegen rules, "don't suggest editing generated clients", API compatibility checks).
2. Review effort level — Low vs. Medium, set by repo admins under Settings → Copilot → Code review. Medium gives more actionable comments with fewer false positives; useful for API/security-sensitive repos.
3. Enable / automatic review — opt in per repo, optionally auto-request review on every PR, or enforce via branch rulesets.
4. Agent skills — .github/skills/ (e.g. a code-review skill) for repo-specific review tasks.

Docs: About Copilot code review · Adding repository custom instructions · Customize code review

Open questions

• Do we want this opt-in per repo, or a shared baseline copilot-instructions.md we maintain centrally and sync?
• Should Copilot reviews be advisory (manual request) or automatic on every PR?
• Concerns about review noise / false positives on a large codebase — start with one repo as a pilot (e.g. pipeline)?

Suggested next steps

• Pilot on one repo with a tailored .github/copilot-instructions.md
• Gather maintainer feedback, then decide on broader rollout + shared instruction baseline

[vdemeester]

As a concrete example, here's a draft .github/copilot-instructions.md tailored to tektoncd/pipeline — focused on its highest-value review concerns (skipping generated/vendored code, enforcing the API compatibility policy and feature gating, reconciler idempotency, and test conventions):

https://gist.github.com/vdemeester/0f3f4eb2511116c396c732c3bb165d72

This could serve as a starting point for a per-repo instruction file, or as input for a shared baseline we maintain centrally.