Add resource sums to terraform plan

- closes #2355

command/hook_count.go

@@ -13,6 +13,11 @@ type CountHook struct {
 	Changed int
 	Removed int
 
+	ToAdd          int
+	ToChange       int
+	ToRemove       int
+	ToRemoveAndAdd int
+
 	pending map[string]countHookAction
 
 	sync.Mutex
@@ -86,3 +91,23 @@ func (h *CountHook) PostApply(
 
 	return terraform.HookActionContinue, nil
 }
+
+func (h *CountHook) PostDiff(
+	n *terraform.InstanceInfo, d *terraform.InstanceDiff) (
+	terraform.HookAction, error) {
+	h.Lock()
+	defer h.Unlock()
+
+	switch d.ChangeType() {
+	case terraform.DiffDestroyCreate:
+		h.ToRemoveAndAdd += 1
+	case terraform.DiffCreate:
+		h.ToAdd += 1
+	case terraform.DiffDestroy:
+		h.ToRemove += 1
+	default:
+		h.ToChange += 1
+	}
+
+	return terraform.HookActionContinue, nil
+}

command/plan.go

@@ -53,6 +53,9 @@ func (c *PlanCommand) Run(args []string) int {
 		}
 	}
 
+	countHook := new(CountHook)
+	c.Meta.extraHooks = []terraform.Hook{countHook}
+
 	ctx, _, err := c.Context(contextOpts{
 		Destroy:   destroy,
 		Path:      path,
@@ -130,6 +133,13 @@ func (c *PlanCommand) Run(args []string) int {
 		ModuleDepth: moduleDepth,
 	}))
 
+	c.Ui.Output(c.Colorize().Color(fmt.Sprintf(
+		"[reset][bold]Plan:[reset] "+
+			"%d to add, %d to change, %d to destroy.",
+		countHook.ToAdd,
+		(countHook.ToChange + countHook.ToRemoveAndAdd),
+		countHook.ToRemove)))
+
 	if detailed {
 		return 2
 	}