Two failure modes wedged the PR-based merge flow (dormant under the
current direct-merge config, but the rollback target):
1. Empty-diff branches ("No commits between ...") were marked `failed`,
pinning the serial merge slot + file leases on a task that is a
legitimate no-op. Now finalized as a terminal DONE via
`finalizeNoOpMergeTask`, mirroring the engine's canonical
`noOpResult` decision (merger-ai.ts).
2. A stale-base PR that GitHub reports CONFLICTING never becomes
mergeable on its own (nothing in the PR path rebases the head), so
`awaiting-pr-checks` waited unbounded — no escape, because the PR
path never incremented `mergeRetries`. Now each conflicting poll
counts against `mergeRetries`, so the existing
`getInReviewStallReason` "merge-retries-exhausted" escape disposes
the task after `maxAutoMergeRetries` cycles. Pending/behind PRs
still wait (checks legitimately run; "behind" is fixed by rebase).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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