Update .gitlab-ci.yml

.gitlab-ci.yml

-# This file is a template, and might need editing before it works on your project.
-# Official docker image.
-image: docker:latest
+# default template
+# The docker image will be named after the branch name
+# Feel free to modify this file in your own branch
 
+image: docker:latest
 services:
   - docker:dind
+  
+variables:
+  CI_REGISTRY_IMAGE: "registry-gitlab.pasteur.fr/dsi-tools/docker-images"
 
+before_script:
+ - docker login -u gitlab-ci-token -p "$CI_BUILD_TOKEN" registry-gitlab.pasteur.fr
+ 
 build:
+  except:
+    - master
   stage: build
   script:
-    - export IMAGE_TAG=$(echo -en $CI_BUILD_REF_NAME | tr -c '[:alnum:]_.-' '-')
-    - docker login -u "gitlab-ci-token" -p "$CI_BUILD_TOKEN" $CI_REGISTRY
-    - docker build --pull -t "$CI_REGISTRY_IMAGE:$IMAGE_TAG" .
-    - docker push "$CI_REGISTRY_IMAGE:$IMAGE_TAG"
+    - docker build --pull -t "$CI_REGISTRY_IMAGE:$CI_BUILD_REF_NAME" .
+    - docker push "$CI_REGISTRY_IMAGE:$CI_BUILD_REF_NAME"