cmd/jujud: implement upgrade-juju command

cmd/juju/main.go

 package main
 
 import (
         "launchpad.net/gnuflag"
         "launchpad.net/juju-core/cmd"
         "os"
 )
 
 // When we import an environment provider implementation
 // here, it will register itself with environs, and hence
@@ skipping 10 matching lines @@
 `
 
 // Main registers subcommands for the juju executable, and hands over control
 // to the cmd package. This function is not redundant with main, because it
 // provides an entry point for testing with arbitrary command line arguments.
 func Main(args []string) {
         juju := &cmd.SuperCommand{Name: "juju", Doc: jujuDoc, Log: &cmd.Log{}}
         juju.Register(&AddUnitCommand{})
         juju.Register(&BootstrapCommand{})
         juju.Register(&DeployCommand{})
-        juju.Register(&DestroyCommand{})
+        juju.Register(&DestroyEnvironmentCommand{})
         juju.Register(&ExposeCommand{})
         juju.Register(&StatusCommand{})
         juju.Register(&UnexposeCommand{})
         juju.Register(&UpgradeJujuCommand{})
         os.Exit(cmd.Main(juju, cmd.DefaultContext(), args[1:]))
 }
 
 func main() {
         Main(os.Args)
 }
 
 func addEnvironFlags(name *string, f *gnuflag.FlagSet) {
         f.StringVar(name, "e", "", "juju environment to operate in")
         f.StringVar(name, "environment", "", "")
 }