Runner: advanced task execution logic

[mjnagel]

Is your feature request related to a problem? Please describe

I have several use cases where I would like to execute a task with more advanced logic wrapping how the task executes. Concrete examples:

• A conditional on whether a task runs, based on a variable/input (noting that this could be done in a script/cmd but not in a wait)
• A loop to run a task multiple times, or the same task name but with different directories/taskfiles

Describe the solution you'd like

I'm not sure what the right approach on this is, for conditionals I think there could be a basic check implemented using conditional on a task to check existence of a variable, and possibly support more advanced logic checks (string equality, etc).

For the loop not really sure what would make sense. I could see a for type syntax being useful, with some ability to change parameter/directory on each. I don't really like the potential gross yaml here.

Describe alternatives you've considered

Most things can be done via cmd with traditional script logic, but this could mean calling uds run inside of a cmd block AND not being able to leverage wait.

[joelmccoy]

Also would like to see a feature that allows conditional execution of actions. I just ran into a scenario where it would be nice to have something like:

tasks:
  - name: validate
    actions:
      - description: Validate the dummy service
        if: $SERVICE_IS_DEPLOYED
        wait:
          cluster:
            kind: Service
            name: dummy-service
            namespace: dummy-namespace

The if keyword could be used to only run the action conditionally. Taking inspiration from github actions. I think this is mainly helpful at the action level, but there may be some other cases where this conditional check would be nice to have at the task level.