fix: store the FULL open-PR set in Status.SourceBranches, not just the delta

[ZacxDev]

Problem (production incident 2026-07-06)

Reconcile polls GitHub for the current open-PR set (newBranches, the FULL list) and then stored only the delta into the authoritative state the downstream pipeline-trigger-operator reads:

pullrequest.Status.SourceBranches.Branches = setDifferences  // only the newly-added branches

Status.SourceBranches is supposed to be the complete set of open PRs. Storing only setDifferences truncates it:

• PR opened (list grows) → stores just the 1 new PR → SourceBranches becomes a partial list of 1.
• PR closed (list shrinks) → setDifferences is empty → SourceBranches becomes empty.

Either way the consumer sees a truncated branch set and rebuilds every open PR (~188 PipelineRuns) despite no new commits, and the next poll re-diffs against the truncated state → endless "New PR received" churn. This is the producer half of the incident; the consumer-side guard already shipped.

Fix

Store the FULL current list while still emitting New PR ... received events only for the genuinely-new PRs. The store-decision is extracted into a tiny pure helper:

func nextSourceBranches(current, polled Branches) (store Branches, newlyAdded []Branch) {
    newlyAdded = current.BranchSetDifference(polled) // events fire only for these
    store = Branches{Branches: polled.Branches}      // authoritative state = FULL polled list
    return
}

Orthogonal to this branch's label-retrigger customization: newBranches already carries the label-folded commit discriminators from the poller, so a label change still shows up as a new entry and still retriggers. No other logic changed.

Test

controllers/pullrequest_controller_helpers_test.go → TestNextSourceBranches drives the helper the way Reconcile does across successive polls (initial population → add → remove) and asserts SourceBranches always equals the FULL polled list while events fire only for genuinely-new PRs.

Verified both directions:

• Passes on the fix.
• Fails on the original delta-only code (temporarily reintroduced): add case stores {c} (want {a,b,c}), remove case stores {} (want {a,b}).

go build ./... and go test ./pkg/... ./api/... ./controllers/... are green. The pre-existing controllers/suite_test.go Ginkgo/envtest suite (TestAPIs) has no specs, so it passes trivially without envtest binaries. CI (.github/workflows/test.yml) gains a targeted go test ./controllers/... -run TestNextSourceBranches step (the full envtest suite is still excluded, as before).

⚠️ Note on other branches

main and gh-conditional-requests carry the identical upstream bug (= setDifferences). This PR only fixes the deployed civitai branch feat/label-retrigger; those branches are not touched here.

🤖 Generated with Claude Code