Version field for kapp app annotations

[ringerc]

Describe the problem/challenge you have

kapp's app deployments track the app's name, but do not record any version for the deployment to show in kapp list etc.

While it is possible to use ytt, kustomize's commonAnnotations etc to inject a kubernetes.io/version annotation into deployed resources, kapp doesn't know to look for it, and no version can be shown in kapp list. It would be immensely useful if kapp list provided an at-a-glance view of deployed component versions.

See fluxcd's flux get kustomization, Helm's helm list for other tools that present at-a-glance component version information.

Describe the solution you'd like

It would be very helpful if kapp deploy took an optional application version flag, which could also be injected as a kapp config stanza. This version would appear in kapp list.

kapp config could also be added that propagates the supplied version to kubernetes.io/version annotations on all components kapp is deploying. This should probably be off by default for compatibility reasons.

Anything else you would like to add:

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[renuy]

Hello @ringerc ,
Could you elaborate on the use case? This could fall in the scope of other tools under carvel, based on what you may be trying to achieve.

[ringerc]

@renuy The goal is at-a-glance visibility of deployed component versions that doesn't require locating some specific resource which may vary from deployed component to deployed component in order to inspect its annotations/labels.

I don't see a clean way to do this w/o support for it in kapp itself.

[100mik]

I am more curious about how such a version would help?
Are you looking to see which set of components were deployed/updated within an app?

If we are talking about a number that is incremented for an entire "app" (if that is what we are talking about when we say component), then how do we consume this? Could this be solved by injecting this value to a config map in each component for example?