ci: Add diff pipeline

.github/workflows/lint-test.yaml

@@ -22,7 +22,7 @@ jobs:
         run: |
           changed=$(ct list-changed --config charts/ct.yaml)
           if [[ -n "$changed" ]]; then
-            echo "::set-output name=changed::true"
+            echo "changed=true" >> "$GITHUB_OUTPUT"
           fi
 
       - name: Run chart-testing (lint)
@@ -34,3 +34,49 @@ jobs:
 
       - name: Run chart-testing (install)
         run: ct install --debug --config charts/ct.yaml --excluded-charts amazon-eks-pod-identity-webhook,keycloak-config-cli
+  diff:
+    name: check diff
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up chart-testing
+        uses: helm/[email protected]
+
+      - name: Run chart-testing (list-changed)
+        id: list-changed
+        run: |
+          changed=$(ct list-changed --config charts/ct.yaml)
+          if [[ -n "$changed" ]]; then
+            echo "changed=true" >> "$GITHUB_OUTPUT"
+            echo "changed_list=\"${changed//$'\n'/ }\"" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: install helm diff plugin
+        if: steps.list-changed.outputs.changed == 'true'
+        run: |
+          helm env
+          helm plugin install https://github.com/databus23/helm-diff --version 3.9.9
+
+      - name: Create kind cluster
+        if: steps.list-changed.outputs.changed == 'true'
+        uses: helm/[email protected]
+
+      - name: Run chart-testing (diff)
+        if: steps.list-changed.outputs.changed == 'true'
+        run: |
+          changed_list=$(echo $changed_list)
+          for chart in $changed_list; do
+            helm install $chart oci://ghcr.io/${{ github.repository_owner }}/charts/$chart --create-namespace --namespace $chart --wait
+            helm diff upgrade $chart charts/$chart \
+              --namespace $chart \
+              --suppress=CustomResourceDefinition \
+              --normalize-manifests \
+              --reset-values \
+              --suppress-output-line-regex="chart: [0-9]" \
+              --suppress-output-line-regex="app.kubernetes.io/version: [0-9]"
+          done