Harden Dependabot auto-merge against races and workflow-file limits#10
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Three PRs merged automatically on the first Dependabot batch, but the initial run also produced transient failures worth eliminating: - Serialize runs with a concurrency group. When several scans finished at once, their merge attempts raced: one won and the others failed against a base branch mid-recomputation. Queuing handles each PR against an up-to-date master. - Merge with a merge commit instead of --squash. A squash re-authors the change as github-actions[bot]; when it touches .github/workflows/**, GitHub refuses it because GITHUB_TOKEN lacks the (ungrantable) 'workflows' permission. A merge commit keeps the edit in Dependabot's own commit, so the token never writes a workflow file. - Retry the merge a few times to ride out transient mergeability recomputation immediately after another PR merges. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_013s3Nae9FEoyZ4bmwMjMtvj
kjake
marked this pull request as ready for review
July 18, 2026 03:55
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Context
The first Dependabot batch (#5–#9) all auto-merged successfully, but the initial concurrent burst also produced transient auto-merge failures. This makes the merge step deterministic so future batches are clean and a workflow-editing PR can never be left stuck.
Changes to
.github/workflows/dependabot-automerge.ymlSerialize with a
concurrencygroup. When several scans finished within seconds of each other, their merge attempts raced — one won and the others failed against a base branch that was still recomputing mergeability. Aconcurrency: { group: dependabot-automerge, cancel-in-progress: false }queues the runs so each PR is handled against an up-to-datemaster.Merge commit instead of
--squash. A squash re-authors the change asgithub-actions[bot]; when that change touches.github/workflows/**, GitHub refuses it with:because
GITHUB_TOKENcan't be granted theworkflowsscope. A merge commit keeps the edit in Dependabot's own commit, so the token never "writes" a workflow file and the merge is allowed.Retry the merge up to 5 times with backoff, to ride out the brief window where a PR's mergeability is still being recomputed right after another PR merges.
Behavior unchanged
Still triggers only on a successful Anchore Container Scan, and still verifies the PR is from
dependabot[bot], targetsmaster, and that the scanned commit is still the PR head before merging. Branch is still deleted after merge.Testing
🤖 Generated with Claude Code
https://claude.ai/code/session_013s3Nae9FEoyZ4bmwMjMtvj
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