Add CI job to fail if README.md needs to be regenerated

.gitlab-ci.yml

@@ -7,6 +7,7 @@ include:
 
 stages:
   - lint
+  - validate
   - test
   - build
   - deploy
@@ -44,6 +45,17 @@ helm_lint:
     - helm dep update .
     - helm lint --strict .
 
+helm_docs_needs_running:
+  stage: validate
+  image: registry.cern.ch/docker.io/jnorwood/helm-docs:v1.14.2
+  rules:
+    - if: '$CI_COMMIT_TAG'
+      when: never
+    - if: $CI_PIPELINE_SOURCE == "push"
+  script:
+    - helm-docs -o test.md
+    - diff -ura test.md README.md
+
 unittest:
   stage: test
   image: registry.cern.ch/docker.io/helmunittest/helm-unittest:3.17.0-0.7.2