Add third party support to kubectl

pkg/kubectl/cmd/explain.go

@@ -52,6 +52,7 @@ func NewCmdExplain(f *cmdutil.Factory, out io.Writer) *cobra.Command {
 		},
 	}
 	cmd.Flags().Bool("recursive", false, "Print the fields of fields (Currently only 1 level deep)")
+	cmdutil.AddInclude3rdPartyFlags(cmd)
 	return cmd
 }
 
@@ -65,7 +66,7 @@ func RunExplain(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []st
 	apiVersionString := cmdutil.GetFlagString(cmd, "api-version")
 	apiVersion := unversioned.GroupVersion{}
 
-	mapper, _ := f.Object()
+	mapper, _ := f.Object(cmdutil.GetIncludeThirdPartyAPIs(cmd))
 	// TODO: After we figured out the new syntax to separate group and resource, allow
 	// the users to use it in explain (kubectl explain <group><syntax><resource>).
 	// Refer to issue #16039 for why we do this. Refer to PR #15808 that used "/" syntax.