CI: stage before we run git-clang-format again

Author: dschwoerer

.github/workflows/clang-format.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Run clang-format
         id: format
         run:
-          while ! git clang-format origin/${{ github.base_ref }} ; do true ; done
+          while ! git clang-format origin/${{ github.base_ref }} ; do git add . ; done
 
       - name: Commit to the PR branch
         uses: stefanzweifel/git-auto-commit-action@v5