ref(helm): add helper to check len of cmd args

cmd/helm/helm.go

 package main
 
 import (
+	"fmt"
 	"os"
+	"strings"
 
 	"github.com/spf13/cobra"
 )
@@ -44,3 +46,14 @@ func init() {
 func main() {
 	RootCommand.Execute()
 }
+
+func checkArgsLength(expectedNum, actualNum int, requiredArgs ...string) error {
+	if actualNum != expectedNum {
+		arg := "arguments"
+		if expectedNum == 1 {
+			arg = "argument"
+		}
+		return fmt.Errorf("This command needs %v %s: %s", expectedNum, arg, strings.Join(requiredArgs, ", "))
+	}
+	return nil
+}

cmd/helm/repo.go

@@ -34,8 +34,8 @@ var repoListCmd = &cobra.Command{
 }
 
 func runRepoAdd(cmd *cobra.Command, args []string) error {
-	if len(args) != 2 {
-		return fmt.Errorf("This command needs two argument, a name for the chart repository and the url of the chart repository")
+	if err := checkArgsLength(2, len(args), "name for the chart repository", "the url of the chart repository"); err != nil {
+		return err
 	}
 
 	err := insertRepoLine(args[0], args[1])