Related issues:
* https://github.com/kubernetes-sigs/kustomize/issues/5031
* https://github.com/kubernetes-sigs/kustomize/issues/5171
After noting this behaviour was not present in
d89b448c74 a `git bisect` pointed to the
change 1b7db20504. The issue with that
change is that upon seeing a `null` node it would replace it with a node
whose value was equivalent but without a `!!null` tag. This meant that
one application of a patch would have the desired approach: the result
would be `null` in the output, but on a second application of a similar
patch the field would be rendered as `"null"`.
To avoid this, define a new attribute on `RNode`s that is checked before
clearing any node we should keep. The added
`TestApplySmPatch_Idempotency` test verifies this behaviour.
See also https://github.com/kubernetes-sigs/kustomize/pull/5365 for an
alternative approach
- When merging (3way) resources use the patch strategy from the openAPI if the definition exists for the field
- Allow disabling of guessing patch strategy merge keys when no definition exists
- Support defining strategy and key directly on configuration fields through line and header coments
- Support attaching schema to parent fields of lists, and propagating -- e.g. that a field is a PodTemplate
