Rework GitLab CI configuration, always build Docker image artifact

This artifact will be used as master-branch and release image, without
building the image again

.gitlab-ci.yml

@@ -17,6 +17,7 @@ before_script:
   - apt-get update
   - apt-get install -y google-chrome-stable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf libxss1 --no-install-recommends
 
+# Build Send, run npm tests
 test:
   stage: test
   script:
@@ -24,48 +25,80 @@ test:
     - npm run lint
     - npm test
 
-# Release Docker image artifact for easy testing
+# Build Docker image, export Docker image artifact
 artifact-docker:
   stage: artifact
   image: docker:latest
+  needs: []
+  services:
+    - docker:dind
+  variables:
+    IMG_FILE: "send:git-$CI_COMMIT_SHA.tar"
+    IMG_NAME: "send:git-$CI_COMMIT_SHA"
+  before_script: []
+  script:
+    - docker build -t $IMG_NAME .
+    - docker image save -o $IMG_FILE $IMG_NAME
+  artifacts:
+    paths:
+      - $IMG_FILE
+    expire_in: 1 week
+
+# Release public Docker image for the master branch
+release-docker-master:
+  stage: release
+  image: docker:latest
+  dependencies:
+    - artifact-docker
   services:
     - docker:dind
   only:
     - master
+  variables:
+    IMG_IMPORT_FILE: "send:git-$CI_COMMIT_SHA.tar"
+    IMG_IMPORT_NAME: "send:git-$CI_COMMIT_SHA"
+    IMG_NAME: "registry.gitlab.com/timvisee/send:master-$CI_COMMIT_SHA"
   before_script: []
   script:
-    - export IMG_NAME=registry.gitlab.com/timvisee/send:master-$CI_COMMIT_SHA
-
     # Login in to registry
     - 'docker login registry.gitlab.com -u $DOCKER_USER -p $DOCKER_PASS'
 
-    # Build and push image, report image name
+    # Load existing, retag for new image images
-    - docker build -t $IMG_NAME .
+    - docker image load -i $IMG_IMPORT_FILE
-    - docker push $IMG_NAME
+    - docker tag $IMG_IMPORT_NAME $IMG_NAME
-    - 'echo Docker image artifact published, available as:'
-    - 'echo "  docker pull $IMG_NAME"'
 
-# Release public Docker image
+    # Publish tagged image
+    - docker push $IMG_NAME
+
+    - 'echo "Docker image artifact published, available as:" && echo "  docker pull $IMG_NAME"'
+
+# Release public Docker image for a version tag
 release-docker:
   stage: release
   image: docker:latest
+  dependencies:
+    - artifact-docker
   services:
     - docker:dind
   only:
     - /^v(\d+\.)*\d+$/
+  variables:
+    IMG_IMPORT_FILE: "send:git-$CI_COMMIT_SHA.tar"
+    IMG_IMPORT_NAME: "send:git-$CI_COMMIT_SHA"
+    IMG_NAME: "registry.gitlab.com/timvisee/send:$CI_COMMIT_REF_NAME"
+    IMG_NAME_LATEST: "registry.gitlab.com/timvisee/send:latest"
   before_script: []
   script:
-    - export IMG_NAME=registry.gitlab.com/timvisee/send:$CI_COMMIT_REF_NAME
-    - export IMG_NAME_LATEST=registry.gitlab.com/timvisee/send:latest
-
     # Login in to registry
     - 'docker login registry.gitlab.com -u $DOCKER_USER -p $DOCKER_PASS'
 
-    # Build and push image, report image name
+    # Load existing, retag for new image images
-    - docker build -t $IMG_NAME .
+    - docker image load -i $IMG_IMPORT_FILE
-    - docker tag $IMG_NAME $IMG_NAME_LATEST
+    - docker tag $IMG_IMPORT_NAME $IMG_NAME
+    - docker tag $IMG_IMPORT_NAME $IMG_NAME_LATEST
+
+    # Publish tagged image
     - docker push $IMG_NAME
     - docker push $IMG_NAME_LATEST
-    - 'echo Docker image artifact published, available as:'
+
-    - 'echo "  docker pull $IMG_NAME_LATEST"'
+    - 'echo "Docker image artifact published, available as:" && echo "  docker pull $IMG_NAME_LATEST" && echo "  docker pull $IMG_NAME"'
-    - 'echo "  docker pull $IMG_NAME"'