ci: add GitLab CI config

.gitlab-ci.yml

@@ -16,10 +16,8 @@ test:
 
 test_and_publish:
   rules:
-    - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
   script:
-    - echo "${DOCKER_TOKEN}"
-    - echo "${DOCKER_USER}"
     - export VERSION=$(grep 'version <-' ascii_alignment_pileup.R | cut -f2 -d'"')
     - export IMAGE="${DOCKER_ORG}/${DOCKER_REPO}"
     - |