plugins: fix usage for plugin commands

Signed-off-by: Tibor Vass <tibor@docker.com>

api/client/plugin/disable.go

@@ -11,7 +11,7 @@ import (
 
 func newDisableCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "disable",
+		Use:   "disable PLUGIN",
 		Short: "Disable a plugin",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {

api/client/plugin/enable.go

@@ -11,7 +11,7 @@ import (
 
 func newEnableCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "enable",
+		Use:   "enable PLUGIN",
 		Short: "Enable a plugin",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {

api/client/plugin/inspect.go

@@ -13,7 +13,7 @@ import (
 
 func newInspectCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "inspect",
+		Use:   "inspect PLUGIN",
 		Short: "Inspect a plugin",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {

api/client/plugin/push.go

@@ -16,7 +16,7 @@ import (
 
 func newPushCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "push",
+		Use:   "push PLUGIN",
 		Short: "Push a plugin",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {

api/client/plugin/remove.go

@@ -13,7 +13,7 @@ import (
 
 func newRemoveCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:     "rm",
+		Use:     "rm PLUGIN",
 		Short:   "Remove a plugin",
 		Aliases: []string{"remove"},
 		Args:    cli.RequiresMinArgs(1),

api/client/plugin/set.go

@@ -12,7 +12,7 @@ import (
 
 func newSetCommand(dockerCli *client.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "set",
+		Use:   "set PLUGIN key1=value1 [key2=value2...]",
 		Short: "Change settings for a plugin",
 		Args:  cli.RequiresMinArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {