use brace expansion for variables

.gitlab-ci.yml

@@ -11,19 +11,19 @@ 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
+  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
+  - docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
 
 build-docker:
   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 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}
   only:
     - master
   only:
@@ -45,10 +45,11 @@ build-binder:
   only:
     - master
 
+
 test-docker:
   stage: test
   script:
-    - docker pull $CONTAINER_TEST_IMAGE
+    - docker pull ${CONTAINER_TEST_IMAGE}
   only:
     - master
   only:
@@ -59,9 +60,9 @@ test-docker:
 release-docker:
   stage: release
   script:
-    - docker pull $CONTAINER_TEST_IMAGE
-    - docker tag $CONTAINER_TEST_IMAGE $CONTAINER_RELEASE_IMAGE
-    - docker push $CONTAINER_RELEASE_IMAGE
+    - docker pull ${CONTAINER_TEST_IMAGE}
+    - docker tag ${CONTAINER_TEST_IMAGE} ${CONTAINER_RELEASE_IMAGE}
+    - docker push ${CONTAINER_RELEASE_IMAGE}
   only:
     - master
   only: