jenkins-job-builder/tests/loader/fixtures/joinlists.yaml

- job:
    name: sample-job
    builders:
      - shell:
        - string-with-comma: !join:
            - ','
            -
                - item1
                - item2
                - item3

        - string-with-space: !join:
            - ' '
            -
                - item1
                - item2
                - item3