Fix metadata update stale checkout (#19222)

Author: trask

.github/workflows/metadata-update.yml

@@ -101,7 +101,18 @@ jobs:
         run: |
           BRANCH_NAME="${{ steps.findbranch.outputs.branch }}"
           git remote set-url origin "https://x-access-token:${GH_TOKEN}@github.com/${{ github.repository }}.git"
-          git commit -m "chore: update instrumentation list [automated]" || echo "No changes to commit."
+          git commit -m "chore: update instrumentation list [automated]"
+          # Metadata collection can run for hours, allowing workflow files on main to change after
+          # checkout. GitHub then rejects pushing the stale branch without workflows: write, even
+          # though the generated commit only changes docs/instrumentation-list.yaml. Merge instead
+          # of rebase so that commit remains tied to its source snapshot while the pushed branch
+          # contains the current workflow files.
+          git fetch origin main
+          if ! git merge --no-edit origin/main; then
+            echo "::error::Failed to merge the latest origin/main into the generated metadata commit."
+            git merge --abort
+            exit 1
+          fi
           git push --force origin "$BRANCH_NAME"
           git remote set-url origin "https://github.com/${{ github.repository }}.git"