ci: add GitLab CI config

.gitlab-ci.yml

@@ -5,13 +5,17 @@ default:
 test:
   rules:
     - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+      when: never
   script:
     - docker build -t testimage:latest .
     - docker run --rm -it testimage:latest tests/test.sh
 
-publish:
+test_and_publish:
   rules:
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+      when: never
   script:
     - export VERSION=$(grep 'version <-' ascii_alignment_pileup.R | cut -f2 -d'"')
     - export IMAGE="${DOCKER_ORG}/${DOCKER_REPO}:${VERSION}"
@@ -23,4 +27,3 @@ publish:
     - docker run --rm -it $IMAGE tests/test.sh
     - echo "${DOCKER_TOKEN}" | docker login -u "${DOCKER_USER}" --password-stdin
     - docker push $IMAGE
-