simplify caching in gitlab-ci

.gitlab-ci.yml

@@ -1,39 +1,24 @@
 image: node:latest
 
 stages:
-    - Preparation
     - Build
     - Test
 
-Install Dependencies:
-    stage: Preparation
 cache:
-        key: $CI_COMMIT_REF_SLUG-$CI_PROJECT_DIR
+    key: ${CI_COMMIT_REF_SLUG}
     paths:
-            - node_modules/
-    script:
-        - npm ci
-    # only:
-    #     changes:
-    #         - package-lock.json
+        - .npm/
+
+before_script:
+    - npm ci --cache .npm --prefer-offline
 
 Build:
     stage: Build
-    cache:
-        key: $CI_COMMIT_REF_SLUG-$CI_PROJECT_DIR
-        paths:
-            - node_modules/
-        policy: pull
     script:
         - npm run build
 
 Lint:
     stage: Test
-    cache:
-        key: $CI_COMMIT_REF_SLUG-$CI_PROJECT_DIR
-        paths:
-            - node_modules/
-        policy: pull
     script:
         - npm run lint
 # Test: