add kubectl diff in common operations (#18665)

content/en/docs/reference/kubectl/overview.md

@@ -79,7 +79,7 @@ Operation       | Syntax    |       Description
 `create`        | `kubectl create -f FILENAME [flags]` | Create one or more resources from a file or stdin.
 `delete`        | `kubectl delete (-f FILENAME \| TYPE [NAME \| /NAME \| -l label \| --all]) [flags]` | Delete resources either from a file, stdin, or specifying label selectors, names, resource selectors, or resources.
 `describe`    | `kubectl describe (-f FILENAME \| TYPE [NAME_PREFIX \| /NAME \| -l label]) [flags]` | Display the detailed state of one or more resources.
-`diff`        | `kubectl diff -f FILENAME [flags]`| Diff file or stdin against live configuration (**BETA**)
+`diff`        | `kubectl diff -f FILENAME [flags]`| Diff file or stdin against live configuration
 `edit`        | `kubectl edit (-f FILENAME \| TYPE NAME \| TYPE/NAME) [flags]` | Edit and update the definition of one or more resources on the server by using the default editor.
 `exec`        | `kubectl exec POD [-c CONTAINER] [-i] [-t] [flags] [-- COMMAND [args...]]` | Execute a command against a container in a pod.
 `explain`    | `kubectl explain  [--recursive=false] [flags]` | Get documentation of various resources. For instance pods, nodes, services, etc.
@@ -373,6 +373,16 @@ kubectl logs <pod-name>
 kubectl logs -f <pod-name>
 ```
 
+`kubectl diff` - View a diff of the proposed updates to a cluster.
+
+```shell
+# Diff resources included in "pod.json".
+kubectl diff -f pod.json
+
+# Diff file read from stdin.
+cat service.yaml | kubectl diff -f -
+```
+
 ## Examples: Creating and using plugins
 
 Use the following set of examples to help you familiarize yourself with writing and using `kubectl` plugins: