.github/workflows/diff-pr.yml

@@ -17,12 +17,18 @@ jobs:
     steps:
       - uses: actions/checkout@v4
         with:
+          ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
 
-      - name: worktree base for diff
+      - name: merge base branch
         run: |
+          git config user.email "ci@localhost"
+          git config user.name "CI"
           git fetch origin ${{ github.event.pull_request.base.ref }}
-          git worktree add "$RUNNER_TEMP/base" "origin/${{ github.event.pull_request.base.ref }}"
+          git merge --no-edit origin/${{ github.event.pull_request.base.ref }}
+
+      - name: worktree base for diff
+        run: git worktree add "$RUNNER_TEMP/base" "origin/${{ github.event.pull_request.base.ref }}"
 
       - name: build closures and render diff
         run: |