Test against PR ref not HEAD

Author: CRThaze

.github/workflows/preview-readme.yaml

@@ -17,6 +17,11 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.ref }}
 
+      - name: Save HEAD SHA before helm-docs
+        id: save-sha
+        run: |
+          echo "sha=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
+
       - name: Render helm docs inside the README.md
         uses: losisin/helm-docs-github-action@v1
         with:
@@ -25,7 +30,7 @@ jobs:
       - name: Check for README changes
         id: check-changes
         run: |
-          if git diff --quiet HEAD -- README.md
+          if git diff --quiet ${{ steps.save-sha.outputs.sha }} -- README.md
           then
             echo "has_changes=false" >> $GITHUB_OUTPUT
           else
@@ -37,7 +42,7 @@ jobs:
         if: steps.check-changes.outputs.has_changes == 'true'
         run: |
           echo 'diff<<EOF' >> $GITHUB_OUTPUT
-          git diff HEAD -- README.md >> $GITHUB_OUTPUT
+          git diff ${{ steps.save-sha.outputs.sha }} -- README.md >> $GITHUB_OUTPUT
           echo 'EOF' >> $GITHUB_OUTPUT
 
       - name: Find and hide outdated comments