fix(ci): never auto-merge an untested head in dependabot-auto-merge#29
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Pass --match-head-commit to `gh pr merge` so the merge is refused if Dependabot rebases the PR after the test run we validated. Without it, a rebase between the test-result check and the merge could land an untested head on main. Add a 30-minute job timeout so the test-polling loop can't hang, and correct the rationale comment: main is protected (signed commits, linear history, PR required) but has no required status checks, which is why the test gate is enforced in this workflow rather than by branch protection.
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Problem
The dependabot auto-merge workflow validates that the test run for the PR's
head.shasucceeded, then merges. But between that check andgh pr merge, Dependabot can rebase the PR onto a new head. The merge would then land a head we never tested.The rationale comment was also stale — it claimed the workflow avoids branch protection because other workflows push directly to
main. That's no longer true: the style check is read-only and the changelog update is PR-based, andmainis protected.Fix
--match-head-commit "$HEAD_SHA"togh pr merge. If the head moved after validation, the merge is refused rather than landing an untested commit.timeout-minutes: 30to the job so the test-polling loop can't hang indefinitely.mainis protected (signed commits, linear history, PR required) but has no required status checks, so the test gate is enforced here in the workflow. A GitHub squash-merge keeps history linear and is signed.No behavioural change for the normal case (tests pass, head unchanged → merge proceeds); it only closes the rebase race.