Mergable inline helm values

[tiagomeireles]

Summary

I'd like to be able to merge inline helm values. Currently, spec.sources.helm.values is defined as a string which doesn't have this ability.

Motivation

Using kustomize, I would like to have a base application with default values. Then patch cluster-specific values using overlays.

Take this example, today, I don't have a way to replace autoDiscovery.clusterName with a different value. Kustomize's patch will replace spec.source.helm.values entirely.

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: helm-guestbook
  namespace: argocd
spec:
  destination:
    namespace: helm-guestbook
    server: https://kubernetes.default.svc
  project: default
  source:
    helm:
      releaseName: cluster-autoscaler
      values: |
        autoDiscovery:
          clusterName: 'foo'
        extraArgs:
          balance-similar-node-groups: true
          skip-nodes-with-system-pods: false
    repoURL: https://kubernetes.github.io/autoscaler
    targetRevision: 9.9.2

Proposal

How do you think this should be implemented?

I don't have strong opinions on implementations. I see three options:

1. Introduce a new field.
2. Changing the existing field type.
3. Do nothing.

Each come with their own pro/cons.

[tiagomeireles]

Duplicate of #2936. Closing as I didn't find that before submitting.