cmd: fix deprecation warning bug

Some kubectl commands were deprecated but would fail to print the
correct warning message when a flag was given before the command name.

	# Correctly prints the warning that "resize" is deprecated and
	# "scale" is now preferred.
	kubectl scale [...]

	# Should print the same warning but no warning is printed.
	kubectl --v=1 scale [...]

This was due to a fragile check on os.Args[1].

This commit implements a new function deprecatedCmd() that is used to
construct new "passthrough" commands which are marked as deprecated and
hidden.

Note that there is an existing "filters" system that may be preferable
to the system created in this commit. I'm not sure why the "filters"
array was not used for all deprecated commands in the first place.

pkg/kubectl/cmd/clusterinfo.go

@@ -19,7 +19,6 @@ package cmd
 import (
 	"fmt"
 	"io"
-	"os"
 	"strconv"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -29,7 +28,7 @@ import (
 	"k8s.io/kubernetes/pkg/kubectl/resource"
 	"k8s.io/kubernetes/pkg/util/i18n"
 
-	"github.com/daviddengcn/go-colortext"
+	ct "github.com/daviddengcn/go-colortext"
 	"github.com/spf13/cobra"
 )
 
@@ -45,9 +44,7 @@ var (
 
 func NewCmdClusterInfo(f cmdutil.Factory, out io.Writer) *cobra.Command {
 	cmd := &cobra.Command{
-		Use: "cluster-info",
-		// clusterinfo is deprecated.
-		Aliases: []string{"clusterinfo"},
+		Use:     "cluster-info",
 		Short:   i18n.T("Display cluster info"),
 		Long:    longDescr,
 		Example: clusterinfoExample,
@@ -62,10 +59,6 @@ func NewCmdClusterInfo(f cmdutil.Factory, out io.Writer) *cobra.Command {
 }
 
 func RunClusterInfo(f cmdutil.Factory, out io.Writer, cmd *cobra.Command) error {
-	if len(os.Args) > 1 && os.Args[1] == "clusterinfo" {
-		printDeprecationWarning("cluster-info", "clusterinfo")
-	}
-
 	client, err := f.ClientConfig()
 	if err != nil {
 		return err