Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -6,8 +6,18 @@ services:
 before_script:
   - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
 
+build-master:
+  stage: build
+  script:
+    - docker build --pull -t "$CI_REGISTRY_IMAGE" .
+    - docker push "$CI_REGISTRY_IMAGE"
+  only:
+    - master
+
 build:
   stage: build
   script:
     - docker build --pull -t "$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG" .
     - docker push "$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG"
+  except:
+    - master