Use Args in cobra.Command to validate args.

Also re-use context.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

required.go

@@ -2,30 +2,19 @@ package cli
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/spf13/cobra"
 )
 
-// MinRequiredArgs checks if the minimum number of args exists, and returns an
-// error if they do not.
-func MinRequiredArgs(args []string, min int, cmd *cobra.Command) error {
-	if len(args) >= min {
+// NoArgs validate args and returns an error if there are any args
+func NoArgs(cmd *cobra.Command, args []string) error {
+	if len(args) == 0 {
 		return nil
 	}
 
-	return fmt.Errorf(
-		"\"%s\" requires at least %d argument(s).\n\nUsage:  %s\n\n%s",
-		cmd.CommandPath(),
-		min,
-		cmd.UseLine(),
-		cmd.Short,
-	)
-}
-
-// AcceptsNoArgs returns an error message if there are args
-func AcceptsNoArgs(args []string, cmd *cobra.Command) error {
-	if len(args) == 0 {
-		return nil
+	if cmd.HasSubCommands() {
+		return fmt.Errorf("\n" + strings.TrimRight(cmd.UsageString(), "\n"))
 	}
 
 	return fmt.Errorf(
@@ -35,3 +24,19 @@ func AcceptsNoArgs(args []string, cmd *cobra.Command) error {
 		cmd.Short,
 	)
 }
+
+// RequiresMinArgs returns an error if there is not at least min args
+func RequiresMinArgs(min int) cobra.PositionalArgs {
+	return func(cmd *cobra.Command, args []string) error {
+		if len(args) >= min {
+			return nil
+		}
+		return fmt.Errorf(
+			"\"%s\" requires at least %d argument(s).\n\nUsage:  %s\n\n%s",
+			cmd.CommandPath(),
+			min,
+			cmd.UseLine(),
+			cmd.Short,
+		)
+	}
+}