feat: adhoc chart dependencies

[mumoshu]

Shameless plug: Adding helm-x integration to helmfile would allow you to add chart dependencies to your local or remote chart without modifying or forking it.

repositories:
- name: stable
  url: https://kubernetes-charts.storage.googleapis.com

releases:
- name: myapp
   chart: charts/mychart
   # version is required because it isn't provided by kustomization by its nature!
   version: 1.2.3
  dependencies:
  - name: envoy
     chart: stable/envoy
     version: 1.5

The dependencies setting results in running helm x upgrade --adhoc-dependenci envoy=stable/envoy:1.5 ...onhelmfile syncfor example, that has the same effect as adding the dependency torequirements.yamlofcharts/mychart`.

See https://github.com/mumoshu/helm-x for more information.

[mumoshu]

This is an advanced use-case you don't usually need. My own use-case for this is for weaveworks/flagger.

Flagger needs a Canary custom resource linked to your K8s deployment and service to function. According to the example, the standard way to add such Canary resource to your chart is to modify (or fork it's not maintained by you) the chart to enable creation of a Cananary resource when the value canary.enabled is set to true:

• https://docs.flagger.app/tutorials/canary-helm-gitops#install
• https://github.com/weaveworks/flagger/blob/master/charts/podinfo/values.yaml#L18-L47

How does feature helps it? It's just easier than forking or modifying chart to get the job done.

That is, I believe you can create a canary chart that its whole purpose is to create a Canary resource. Adding the canary chart to the adhoc dependencies of your app charts allows you to include Canary resources into your apps' helm releases, without ever modifying them all.