cmd/options: kubectl options writes to out stream

Previous behavior was to write to stderr (thanks to the fallback system
in the Cobra library), which made it difficult to grep for flags.

For example:

	kubectl options | grep recursive

federation/pkg/kubefed/kubefed.go

@@ -67,7 +67,7 @@ func NewKubeFedCommand(f cmdutil.Factory, in io.Reader, out, err io.Writer, defa
 	templates.ActsAsRootCommand(cmds, filters, groups...)
 
 	cmds.AddCommand(kubectl.NewCmdVersion(f, out))
-	cmds.AddCommand(kubectl.NewCmdOptions())
+	cmds.AddCommand(kubectl.NewCmdOptions(out))
 
 	return cmds
 }

pkg/kubectl/cmd/cmd.go

@@ -378,7 +378,7 @@ func NewKubectlCommand(f cmdutil.Factory, in io.Reader, out, err io.Writer) *cob
 	cmds.AddCommand(NewCmdVersion(f, out))
 	cmds.AddCommand(NewCmdApiVersions(f, out))
 	cmds.AddCommand(deprecatedAlias("apiversions", NewCmdApiVersions(f, out)))
-	cmds.AddCommand(NewCmdOptions())
+	cmds.AddCommand(NewCmdOptions(out))
 
 	return cmds
 }

pkg/kubectl/cmd/options.go

@@ -17,6 +17,8 @@ limitations under the License.
 package cmd
 
 import (
+	"io"
+
 	"k8s.io/kubernetes/pkg/kubectl/cmd/templates"
 	"k8s.io/kubernetes/pkg/util/i18n"
 
@@ -30,7 +32,7 @@ var (
 )
 
 // NewCmdOptions implements the options command
-func NewCmdOptions() *cobra.Command {
+func NewCmdOptions(out io.Writer) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:     "options",
 		Short:   i18n.T("Print the list of flags inherited by all commands"),
@@ -41,7 +43,13 @@ func NewCmdOptions() *cobra.Command {
 		},
 	}
 
-	templates.UseOptionsTemplates(cmd)
+	// The `options` command needs write its output to the `out` stream
+	// (typically stdout). Without calling SetOutput here, the Usage()
+	// function call will fall back to stderr.
+	//
+	// See https://github.com/kubernetes/kubernetes/pull/46394 for details.
+	cmd.SetOutput(out)
 
+	templates.UseOptionsTemplates(cmd)
 	return cmd
 }