Trigger cicd pipeline after merge request accept on master, Gitlab
https://docs.gitlab.com/ee/ci/yaml/

https://gitlab.com/gitlab-org/gitlab-ce/issues/31296#note_34944784


integration-testing:
  stage: test
  only:
    - master
  script:
    - ./gradlew clean build asciidoctor



Another option is to create a webhook

https://gitlab.scm.webanywhere.co.uk/help/user/project/integrations/webhooks.md

If the "Merge request events" is clicked one could trigger a pipeline if a Pull Request gets updated, created or merged.