Use deploy key for issue_comment workflow

.github/workflows/format-pr.yml

@@ -19,6 +19,8 @@ jobs:
         with:
           # Credentials needed for pushing changes at the end.
           # This is already the default, but for safety we are being explicit about this.
+          # Commits made by workflow_dispatch trigger will trigger new workflows to run,
+          # so don't need to use SSH deploy key.
           persist-credentials: true
       - name: Install Node.js
         uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af
@@ -91,8 +93,11 @@ jobs:
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           repository: TurboWarp/extensions
-          # Credentials needed at the end to do the push.
-          persist-credentials: true
+          # Commits made using the default token in an issue_comment trigger won't cause more
+          # workflows to run, so any commits it pushes will be stuck in limbo forever waiting
+          # for workflows to run that will never run. To workaround this, we use an SSH key
+          # instead. It's a GitHub deploy key so it's scoped only to this repository.
+          ssh-key: ${{ secrets.FORMAT_PR_DEPLOY_KEY }}
       - name: Checkout pull request
         run: gh pr checkout "$PR_NUM"
         env: