allow to opt-out from automated Environment stopping when a branch gets deleted

Problem to solve

CI/CD Environments might have a stop action defined, so a cleanup job is triggered when the Environment is stopped. While this can be done manually, it is triggered automatically if the corresponding branch is deleted.

Users might want to stop Environments (deployments in this case), even productive ones exclusively on a manual basis, so the Environment lifecycle is independent from merging a branch.

Intended users

Unknown

Further details

Even though this behavior is documented, it is imho unexpected that Environments are stopped automatically.
- on_stop in .gitlab_ci.yml behaves as on_stop_or_branch_remove 😉
Especially in smaller projects, common DEV/UAT environments might be prepared / defined in feature branches and should survive being merged after the MR got accepted by the responsible team members.

Proposal

Permissions and Security

No need for changes.

Documentation

Currently, the on_stop action is responsible for defining a stop action and the current behavior. In order not to break the current behaviour, I would add an optional property keep_running to the environment block like

my deployment:
  stage: deploy
  script: make deploy-app
  environment:
    name: my-env
    on_stop: stop_app
    # if this is defined and set to 'true', the environment is not stopped
    # when its defining feature branch got removed
    keep_running: true

Testing

The risk or drawback is to have the .gitlab-ci.yml syntax extended, which will require additional tests.

What does success look like, and how can we measure that?

Success: An environment is not stopped after its feature branch is deleted iff the keep_running property is defined on the environment and set to true.