Change the way aliases to subcommands are handled.

cmd/juju/unexpose.go

 package main
 
 import (
         "errors"
 
         "launchpad.net/gnuflag"
         "launchpad.net/juju-core/cmd"
         "launchpad.net/juju-core/juju"
 )
 
 // UnexposeCommand is responsible exposing services.
 type UnexposeCommand struct {
         EnvName     string
         ServiceName string
 }
 
 func (c *UnexposeCommand) Info() *cmd.Info {
-        return &cmd.Info{"unexpose", "", "unexpose a service", ""}
+        return &cmd.Info{
+                Name:    "unexpose",
+                Args:    "<service>",
+                Purpose: "unexpose a service",
+        }
 }
 
 func (c *UnexposeCommand) SetFlags(f *gnuflag.FlagSet) {
         addEnvironFlags(&c.EnvName, f)
 }
 
 func (c *UnexposeCommand) Init(args []string) error {
         if len(args) == 0 {
                 return errors.New("no service name specified")
         }
         c.ServiceName = args[0]
         return cmd.CheckEmpty(args[1:])
 }
 
 // Run changes the juju-managed firewall to hide any
 // ports that were also explicitly marked by units as closed.
 func (c *UnexposeCommand) Run(_ *cmd.Context) error {
         conn, err := juju.NewConnFromName(c.EnvName)
         if err != nil {
                 return err
         }
         defer conn.Close()
         svc, err := conn.State.Service(c.ServiceName)
         if err != nil {
                 return err
         }
         return svc.ClearExposed()
 }