Reuse strategic merge patches for multiple targets

[hyww]

It seems that we cannot reuse strategic merge patches for multiple targets since targets are defined inside each patch.

I've come up with an idea that maybe we can put strategic merge patches in List and reuse duplicated part of patches using anchor/reference of YAML.

#637 is my implementation and below is an example to apply hostAliases patch to multiple Deployments

apiVersion: v1
kind: List
items:
- apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: deployment-a
  spec: &hostAliases
    template:
      spec:
        hostAliases:
        - hostnames:
          - a.example.com
          ip: 1.1.1.1
        - hostnames:
          - b.example.com
          ip: 8.8.8.8
- apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: deployment-b
  spec: *hostAliases

If this seems to be a correct method to deal with the problem, I might be able to work on this further and provide tests, documentations, examples, etc.

[Liujingfang1]

This is another issue for List, which is to load resources from a List #581

[Liujingfang1]

fixed by #637