Include review comments

Author: Ke Zhu

docs/design_proposals/configurable-transformable-allowlist.md

@@ -37,27 +37,47 @@ Option in `skaffold.yaml`
 deploy:
   config:
     transformableAllowList:
-    - Group: example.com
-      Kind: Application
-    - Group: argoproj.io
-      Kind: Workflow
-    - Group: tekton.dev
-      Kind: Task
+    - type: pod # no group, implicitly all versions
+    - type: batch/Job # group, implicitly all versions
+    - type: openfaas.com/v1/Function
+      image: [spec.image]
+      labels: [spec.metadata.labels, spec.labels]    # https://www.openfaas.com/blog/manage-functions-with-kubectl/
+    - type: apps/v1beta1/Deployment
+      image: [spec.template.spec.initContainers.*.image, spec.template.spec.containers.*.image]
+      labels: [spec.metadata.labels, spec.template.metadata.labels]
 ```
 
+The value of `type` field points to a resource type. So it's case sensitive
+and should support API groups and resource versions:
+
+* When not specifying group, it will transform given resource type of any group or versions.
+* When providing group but not resource version, it will transform given
+resource type of any versions.
+
+The value of `labels` field is a list of JSON-path-like paths to apply `labels`
+block to. If no `labels` field configured, it will simply apply `labels` block
+if missing.
+
+The value of `image` field is also a list of JSON-path-like paths to rewrite. If
+no `image` field configured, it will rewrite any field named `image`.
+
 ## Open issues/Questions
 
 Since it is an allowlist, neither options could disable transformation on any
-built-in resource like `ReplicaSet` or `Deployment`.
+built-in resource like `ReplicaSet` or `Deployment`. However, it may need to
+refactor [current allowlist](https://github.com/GoogleContainerTools/skaffold/blob/27c38228ab929ddaf2636637b43f17fda1686652/pkg/skaffold/kubernetes/manifest/visitor.go#L28-L43).
 
 Is there any need to work out a deny list?
 
 ## Implementation plan
 
 1. `pkg/skaffold/schema/latest/v1/config.go` - Add config option
 `transformableAllowList` to `DeployConfig`.
-2. `pkg/skaffold/kubernetes/manifest/visitor.go` - Add new parameter `transformableAllowList` 
-to `*ManifestList.Visit()` by appending it to existing coded `transformableAllowList`
+2. `pkg/skaffold/kubernetes/manifest/visitor.go` - Refactor allowlist and add
+new parameter `transformableAllowList` to `*ManifestList.Visit()` by appending
+it to existing coded `transformableAllowList`
+    - Support `labels` field
+    - Support `image` field
 3. `pkg/skaffold/kubernetes/manifest/images.go` - Add new parameter to `*ManifestList.ReplaceImages()`
 to support given `transformableAllowList`
 4. Instrument each deployer to use the new parameter `transformableAllowList`