Launch nbstripout from pre-commit on each commit. Launch docker build when a...

Launch nbstripout from pre-commit on each commit. Launch docker build when a docker file is modified or on tag. Only push docker images to the registry on tags

.gitlab-ci.yml

 stages:
+  - prepare
   - build
 
 # As suggested by https://blog.sparksuite.com/7-ways-to-speed-up-gitlab-ci-cd-times-29f60aab69f9
 variables:
     DOCKER_DRIVER: overlay2
 
+check_notebooks_empty_outputs:
+    stage: prepare
+    image: python:3.10
+    tags:
+        - ci.inria.fr
+    script:
+        - pip install pre-commit
+        - pre-commit install
+        - pre-commit run --all-files
+
 .build_docker_image: &build_docker_image
     stage: build
     image: docker
     retry: 2
-    only:
-        - web
     tags:
         - ci.inria.fr
     before_script:
         - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
     script:
         # Latest is always generated but not pushed if ${UPDATE_LATEST_TAG} is not "True"
-        - docker build -f docker/Dockerfile.${NAME} -t $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:${TAG} -t $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:latest .
+        - docker build -f docker/Dockerfile.${NAME} -t ${NAME} .
         - docker container prune
-        - docker push $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:${TAG}
-        - if [ "${UPDATE_LATEST_TAG}" == "True" ]; then docker push $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:latest; fi
+        - |
+            if [ $CI_COMMIT_TAG -ne '' ]; then
+                docker tag ${NAME} $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:latest
+                docker push $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:latest
+                docker tag ${NAME} $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:${CI_COMMIT_TAG}
+                docker push $CI_REGISTRY/$CI_PROJECT_PATH/${NAME}:${CI_COMMIT_TAG}
+            fi
+    rules:
+        - if: '$CI_COMMIT_TAG'
+          changes:
+            - docker/Dockerfile.${NAME}
+          when: on_success
 
 
 build_xeus-cling: