Warning user that the active machine was restarted and may have a new IP

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

commands/restart.go

@@ -1,6 +1,10 @@
 package commands
 
 import (
+	"os"
+	"strings"
+
+	"github.com/docker/machine/libmachine"
 	"github.com/docker/machine/log"
 
 	"github.com/codegangsta/cli"
@@ -10,4 +14,58 @@ func cmdRestart(c *cli.Context) {
 	if err := runActionWithContext("restart", c); err != nil {
 		log.Fatal(err)
 	}
+
+	warnIfActiveIPChanged(c)
+}
+
+func warnIfActiveIPChanged(c *cli.Context) {
+	if activeInList(c.Args()) {
+		activeURL := os.Getenv("DOCKER_HOST")
+		log.Debugf("checking to see if active host's URL has changed from %s", activeURL)
+
+		h := getActiveHost(c)
+		u, err := h.GetURL()
+		if err != nil {
+			log.Fatal(err)
+		}
+		if activeURL != u {
+			// TODO: hardcoded port here is a giant kludge...
+			var swarmOpt string
+			if strings.Contains(activeURL, ":3376") {
+				swarmOpt = "--swarm "
+			}
+			log.Warnf("Active machine was restarted, and has a new IP address.\nRun 'eval \"$(docker-machine env %s%s)\"' again.", swarmOpt, h.Name)
+		}
+	}
+}
+
+func activeInList(machines []string) bool {
+	active := os.Getenv("DOCKER_MACHINE_NAME")
+	return active != "" && inArray(active, machines)
+}
+
+func getActiveHost(c *cli.Context) *libmachine.Host {
+	certInfo := getCertPathInfo(c)
+	store, err := getDefaultStore(
+		c.GlobalString("storage-path"),
+		certInfo.CaCertPath,
+		certInfo.CaKeyPath,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	active, err := store.GetActive()
+	if err != nil {
+		log.Fatal(err)
+	}
+	return active
+}
+
+func inArray(s string, a []string) bool {
+	for _, cur := range a {
+		if cur == s {
+			return true
+		}
+	}
+	return false
 }