Use `--` to specify variadic positional arguments

update.diff

diff --git a/api/client/service/update.go b/api/client/service/update.go
index dc6e34c..f35bc17 100644
--- a/api/client/service/update.go
+++ b/api/client/service/update.go
@@ -2,6 +2,7 @@ package service
 
 import (
 	"fmt"
+	"strings"
 	"time"
 
 	"golang.org/x/net/context"
@@ -25,19 +26,26 @@ func newUpdateCommand(dockerCli *client.DockerCli) *cobra.Command {
 	var opts updateOptions
 
 	cmd := &cobra.Command{
-		Use:   "update [OPTIONS] SERVICE [ARG...]",
+		Use:   "update [OPTIONS] SERVICE [--] [ARG...]",
 		Short: "Update a service",
 		Args:  cli.RequiresMinArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			opts.serviceID = args[0]
 			if len(args) > 1 {
-				opts.args = args[1:]
+				if strings.HasPrefix(args[1], "-") && args[1] != "--" {
+					return cmd.Help()
+				} else if args[1] == "--" {
+					opts.args = args[2:]
+				} else {
+					opts.args = args[1:]
+				}
 			}
 			return runUpdate(dockerCli, cmd.Flags(), opts)
 		},
 	}
 
 	flags := cmd.Flags()
+	flags.SetInterspersed(false)
 	flags.String("image", "", "Service image tag")
 	// TODO: make this entrypoint and share with create
 	flags.StringSlice("command", []string{}, "Service command")