Install command batches through one path

registry.go

@@ -5,13 +5,17 @@ import "fmt"
 // Register adds a batch of root commands to the application. The batch is
 // validated before the registry is changed.
 func (a *App) Register(commands ...Command) error {
+	return a.installBatch(commands...)
+}
+
+func (a *App) installBatch(commands ...Command) error {
 	if a == nil {
 		return fmt.Errorf("cannot register commands on a nil app")
 	}
 
 	pending := make(map[string]*commandNode, len(commands))
 	for _, command := range commands {
-		if err := validateCommandDeclaration(command); err != nil {
+		if err := validateCommandPlacement(command); err != nil {
 			return err
 		}
 		if command.record.absent {