title: Trigger Gitlab-CI Pipeline only when there is a new tag
body: <p>I have following gitlab-ci conf. file:</p>
  
  <pre><code>before_script:
    - echo %CI_BUILD_REF%
    - echo %CI_PROJECT_DIR%
  
  stages:
    - createPBLs
    - build
    - package
  
  
  create PBLs:
    stage: createPBLs
    script: 
      - xcopy /y /s "%CI_PROJECT_DIR%" "C:\Bauen\"
      - cd "C:\Bauen\"
      - ./run_orcascript.cmd
  
  
  build:
    stage: build
    script:
    - cd "C:\Bauen\"
    - ./run_pbc.cmd
    except:
    - master
  
  build_master:
    stage: build
    script:
    - cd "C:\Bauen\"
    - ./run_pbcm.cmd
    only:
    - master
  
  package:
    stage: package
    script:
    - cd "C:\Bauen\"
    - ./cpfiles.cmd
    artifacts:
      expire_in: 1 week
      name: "%CI_COMMIT_REF_NAME%"
      paths:
        - GitLab-Build
  </code></pre>
  
  <p>How can I add the rule that the pipeline will ONLY trigger if a new tag has been added to a branch? The tag should start with "Ticket/ticket_"</p>
  
  <p>Currently he is building for every push.</p>