simplify CI config

.gitlab-ci.yml

@@ -4,56 +4,24 @@ services:
 
 stages:
   - build
-  - test
-  - release
 
 variables:
   GIT_SUBMODULE_STRATEGY: recursive
-  DOCKER_HOST: tcp://docker:2376 # Use TLS https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#tls-enabled
   DOCKER_TLS_CERTDIR: "/certs"
-  CONTAINER_TEST_IMAGE: ${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}
-  CONTAINER_RELEASE_IMAGE: ${CI_REGISTRY_IMAGE}:latest
 
 before_script:
   - docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
 
-build-docker:
+build:
   stage: build
   script:
     - docker pull ${CONTAINER_TEST_IMAGE} || true
-    - docker build --cache-from ${CONTAINER_TEST_IMAGE} --tag ${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHA} --tag ${CONTAINER_TEST_IMAGE} .
-    - docker push ${CI_REGISTRY_IMAGE}:${CI_COMMIT_SHA}
-    - docker push ${CONTAINER_TEST_IMAGE}
+    - docker build --cache-from ${CONTAINER_TEST_IMAGE}
+                   --tag ${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}
+                   --tag ${CI_REGISTRY_IMAGE}:latest .
+    - docker push ${CI_REGISTRY_IMAGE}:${CI_COMMIT_REF_SLUG}
+    - docker push ${CI_REGISTRY_IMAGE}:latest
   only:
     - master
-  only:
-    changes:
-      - Dockerfile
-  tags:
-    - docker
-
-test-docker:
-  stage: test
-  script:
-    - docker pull ${CONTAINER_TEST_IMAGE}
-  only:
-    - master
-  only:
-    changes:
-      - Dockerfile
-  tags:
-    - docker
-
-release-docker:
-  stage: release
-  script:
-    - docker pull ${CONTAINER_TEST_IMAGE}
-    - docker tag ${CONTAINER_TEST_IMAGE} ${CONTAINER_RELEASE_IMAGE}
-    - docker push ${CONTAINER_RELEASE_IMAGE}
-  only:
-    - master
-  only:
-    changes:
-      - Dockerfile
   tags:
     - docker