[workflows] Always pull code-format-helper.py from the main branch

After bc06cd5 we started pulling
code-fromat-helper.py from the pull request branch, but if the pull
request branch is not up-to-date, then the job will fail, because
this workflow is incompatible with the old version of the script.

In order to fix this, we need to pull the script from the main branch
like we were doing before to ensure that it always gets the latest
version of the script.

Author: tstellar

.github/workflows/pr-code-format.yml

@@ -25,6 +25,20 @@ jobs:
           separator: ","
           skip_initial_fetch: true
 
+      # We need to pull the script from the main branch, so that we ensure
+      # we get a version of the script that supports the --wirte-comment-to-file
+      # option.
+      - name: Fetch code formatting utils
+        uses: actions/checkout@v4
+        with:
+          reository: ${{ github.repository }}
+          ref: ${{ github.base_ref }}
+          sparse-checkout: |
+            llvm/utils/git/requirements_formatting.txt
+            llvm/utils/git/code-format-helper.py
+          sparse-checkout-cone-mode: false
+          path: code-format-tools
+
       - name: "Listed files"
         env:
           CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
@@ -42,10 +56,10 @@ jobs:
         with:
           python-version: '3.11'
           cache: 'pip'
-          cache-dependency-path: 'llvm/utils/git/requirements_formatting.txt'
+          cache-dependency-path: 'code-format-tools/llvm/utils/git/requirements_formatting.txt'
 
       - name: Install python dependencies
-        run: pip install -r llvm/utils/git/requirements_formatting.txt
+        run: pip install -r code-format-tools/llvm/utils/git/requirements_formatting.txt
 
       - name: Run code formatter
         env:
@@ -58,7 +72,7 @@ jobs:
         # explicitly in code-format-helper.py and not have to diff starting at
         # the merge base.
         run: |
-          python ./llvm/utils/git/code-format-helper.py \
+          python ./code-format-tools/llvm/utils/git/code-format-helper.py \
             --write-comment-to-file \
             --token ${{ secrets.GITHUB_TOKEN }} \
             --issue-number $GITHUB_PR_NUMBER \