fix: retry gh transient 404 on check-run update

[chmouel]

📝 Description of the Change

GitHub can answer with a 404 when Pipelines-as-Code updates a check run
it just created, causing PAC to abort PipelineRun creation and leave
the pull request with a failed check that /retest cannot recover
when triggering is restricted to pull_request events.

This fix creates the check run fully formed (output, annotations, and
conclusion when already finished) in a single call, so a freshly
created check run no longer needs an immediate follow-up update. For
check runs whose id is restored from a PipelineRun annotation, the
update is retried on an explicit 404 with a short exponential backoff
(500ms, 1s, 2s), since another reconcile may have created that check
run only moments earlier and GitHub can still report it missing.

Every other 404 remains terminal: an id discovered through a
check-run lookup, or a transport error/timeout, is never retried, so
deleted or inaccessible check runs and requests that may have already
reached GitHub still surface as errors instead of being retried
unsafely.

🔗 Linked GitHub Issue

Fixes #2920
Jira: SRVKP-13334

🧪 Testing Strategy

• Unit tests
• Integration tests
• End-to-end tests
• Manual testing
• Not Applicable

Comprehensive unit tests were added covering:

• Successful retry recovery from transient 404s
• Terminal 404s for non-created check runs
• Server errors and context cancellation
• Exponential backoff timing

🤖 AI Assistance

• I have used AI assistance for this PR.

This PR involved AI-assisted code generation and refinement. The implementation has been thoroughly reviewed and tested to ensure it meets the project's standards and correctly handles the edge cases around check-run creation and update retries.

✅ Submitter Checklist

• 📝 My commit messages are clear, informative, and follow the project's How to write a git commit message guide. The Gitlint linter ensures in CI it's properly validated
• ✨ I have ensured my commit message prefix (e.g., fix:, feat:) matches the "Type of Change" I selected above.
• ♽ I have run make test and make lint locally to check for and fix any issues.
• 📖 I have added or updated documentation for any user-facing changes.
• 🧪 I have added sufficient unit tests for my code changes.
• 🎁 I have added end-to-end tests where feasible. See README for more details.
• 🔎 I have addressed any CI test flakiness or provided a clear reason to bypass it.
• If adding a provider feature, I have filled in the following and updated the provider documentation:
  • GitHub App
  • GitHub Webhook
  • Gitea/Forgejo
  • GitLab
  • Bitbucket Cloud
  • Bitbucket Data Center

[codecov]

Codecov Report

❌ Patch coverage is 90.74074% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.71%. Comparing base (aeed7ee) to head (82afba7).

Files with missing lines	Patch %	Lines
pkg/provider/github/status.go	90.74%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2922      +/-   ##
==========================================
+ Coverage   80.66%   80.71%   +0.04%     
==========================================
  Files         164      164              
  Lines       13910    13937      +27     
==========================================
+ Hits        11221    11249      +28     
  Misses       1967     1967              
+ Partials      722      721       -1     

Flag	Coverage Δ
unit-tests	80.71% <90.74%> (+0.04%)	⬆️

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[pipelines-as-code]

Paco Review ✅

This PR adds a targeted retry mechanism in the GitHub provider so that a check-run update returning HTTP 404 immediately after Pipelines-as-Code itself created that check run is retried a few times with exponential backoff, instead of failing outright, since GitHub can briefly report a freshly-created check run as missing. It introduces isNotFoundError and updateCheckRun helpers, wires a new createdNow flag through getOrUpdateCheckRunStatus to gate the retry to only just-created check runs, adds a defensive nil check for checkRunID, and includes new table-driven tests plus a configmap documentation update describing the behavior.

Review difficulty: 3/5 (Moderate) — The change is moderate in size but touches a core, widely-used status-update path and introduces new retry/timing logic that needs careful validation of edge cases and test determinism.

No new review comments found at this time. Nice work!

_{Reviewed commit: 727bd28}

[Copilot]

Pull request overview

This PR improves reliability of the GitHub provider by retrying only the check-run update call when GitHub returns a transient HTTP 404 immediately after Pipelines-as-Code created the check run in the same operation (to mitigate GitHub read-after-write lag), while keeping all other 404s terminal.

Changes:

• Add isNotFoundError and updateCheckRun(...) helper to retry Checks.UpdateCheckRun on explicit 404 with short exponential backoff (500ms, 1s, 2s) when the check run was created “now”.
• Wire getOrUpdateCheckRunStatus to call the new retrying helper only for newly-created check runs.
• Add unit tests covering retry/no-retry behavior, context cancellation, and 404 detection; document this retry behavior in the configmap API docs.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pkg/provider/github/status.go	Adds explicit 404 detection and a bounded backoff retry for check-run update only when the check run was created in the same operation.
pkg/provider/github/status_test.go	Adds focused tests for the new retry behavior and helper logic using a fake clock and GitHub test server.
docs/content/docs/api/configmap.md	Documents the always-on GitHub transient-404 retry for immediate post-create check-run updates.

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