GitLab review apps: a fresh environment per merge request

Spin up an ephemeral deploy for every merge request and tear it down on merge — review real changes, not screenshots.

A review app is a full, running deploy of a branch, created when a merge request opens and destroyed when it merges or closes. Reviewers click a link and use the actual change instead of imagining it from a diff. GitLab builds this from two pipeline jobs and a dynamic environment.

Deploy on merge request

review:
  stage: deploy
  script:
    - helm upgrade --install mr-$CI_MERGE_REQUEST_IID ./chart \
        --set host=$CI_COMMIT_REF_SLUG.review.acme.dev
  environment:
    name: review/$CI_COMMIT_REF_SLUG
    url: https://$CI_COMMIT_REF_SLUG.review.acme.dev
    on_stop: stop_review
  rules:
    - if: $CI_MERGE_REQUEST_IID

Tear it down automatically

stop_review:
  stage: deploy
  script:
    - helm uninstall mr-$CI_MERGE_REQUEST_IID
  environment:
    name: review/$CI_COMMIT_REF_SLUG
    action: stop
  rules:
    - if: $CI_MERGE_REQUEST_IID
      when: manual

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