[Vivswan]

Before

      - name: Format (biome) and stage the patch
        id: format
        run: |
          # The patch belongs to this commit alone; the push job refuses any other head.
          echo "head=$(git rev-parse HEAD)" >> "$GITHUB_OUTPUT"
          bun run lint:fix
          # Anything the formatter left staged is not this workflow's fix: start from an empty index, then stage
          # modifications and deletions of tracked files alone (a formatter adds nothing).
          git reset -q
          git add -u
          git diff --cached --binary > "$RUNNER_TEMP/format.patch"
          if [ -s "$RUNNER_TEMP/format.patch" ]; then
            git diff --cached --stat
            echo "changed=true" >> "$GITHUB_OUTPUT"
          else
            echo "nothing to format"
            echo "changed=false" >> "$GITHUB_OUTPUT"
          fi

After

      - name: Format (biome) and stage the patch
        id: format
        run: bun .github/scripts/auto-format-steps.ts format

How

• The block is the format subcommand of auto-format-steps.ts: the same commands, outputs, log line, and patch file.
• One deviation on a runner: a failed git rev-parse HEAD ends the step with git's status, where the shell wrote an empty head=.
• Two more only off a runner: an unset RUNNER_TEMP ends the step before any patch, and a patch file removed under the step ends it instead of reading changed=false.
• Library: biome confines @actions/core to src/action/ and the push job that runs this file installs nothing, so the repo's helpers stay.

Proof

• Tests: bun test test/scripts/auto-format-steps.test.ts test/workflows/repo-owned-workflows.test.ts 16 pass (3 new, red before the subcommand existed).
• Census: grep -c 'run: |' .github/workflows/auto-format.yml 1 before, 0 after.
• Gates: typecheck, biome, actionlint clean. Codex review converged.

Technical details

• The new tests pin git's staging semantics and bun's exit propagation: what reset -q plus add -u admits to the patch (modifications and deletions of tracked files, never an addition, staged earlier or made by the formatter), and that a failing formatter stops the step after head= with the formatter's status and no patch file.
• The format job runs this file from the PR branch's checkout, as it ran the shell block: that job holds no write token, and the push job still runs its copy from the default branch.
• Line accounting (git diff --numstat origin/main...HEAD): script +29/-6, workflow +1/-16, test +65/-2.
• Files: .github/scripts/auto-format-steps.ts, .github/workflows/auto-format.yml, test/scripts/auto-format-steps.test.ts.

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused refactor preserves existing behavior and includes coverage for its key paths.

Review effort: Balanced
Findings: None

What changed in this PR

Moves auto-format workflow logic into the shared step script while preserving patch and output behavior.

Changes:

• Adds the format script subcommand.
• Simplifies the workflow step.
• Tests staging, no-op, and failure behavior.

File	Description
.github/​scripts/​auto-format-steps.ts	Implements the format subcommand.
.github/​workflows/​auto-format.yml	Invokes the new subcommand.
test/​scripts/​auto-format-steps.test.ts	Covers format-step behavior.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The extracted behavior matches the workflow logic and is covered by focused tests.

Review effort: Balanced
Findings: None

[Copilot]

Copilot review overview

🟢 Approval recommended

The refactor preserves the workflow semantics and has focused coverage for success and failure paths.

Review effort: Balanced
Findings: None