etcdctl/ctlv3: clarify 'user add' argument (user:password)

etcdctl/README.md

@@ -1074,7 +1074,7 @@ ROLE is used to specify differnt roles which can be assigned to etcd user(s).
 
 USER provides commands for managing users of etcd.
 
-### USER ADD \<user name\> [options]
+### USER ADD \<user name or user:password\> [options]
 
 `user add` creates a user.
 

etcdctl/ctlv3/command/user_command.go

@@ -51,7 +51,7 @@ var (
 
 func newUserAddCommand() *cobra.Command {
 	cmd := cobra.Command{
-		Use:   "add <user name> [options]",
+		Use:   "add <user name or user:password> [options]",
 		Short: "Adds a new user",
 		Run:   userAddCommandFunc,
 	}