only save state if has changes

main.go

@@ -53,16 +53,23 @@ type App struct {
 }
 
 func (a *App) Save() error {
+	hasChanges := false
 	for id, grain := range a.pool.GetGrains() {
 		if grain == nil {
 			continue
 		}
-		log.Printf("Saving grain %s\n", id)
-		err := a.storage.Store(id, grain)
-		if err != nil {
-			log.Printf("Error saving grain %s: %v\n", id, err)
+		if grain.GetLastChange() > a.storage.LastSaves[id] {
+			hasChanges = true
+			log.Printf("Saving grain %s\n", id)
+			err := a.storage.Store(id, grain)
+			if err != nil {
+				log.Printf("Error saving grain %s: %v\n", id, err)
+			}
 		}
 	}
+	if !hasChanges {
+		return nil
+	}
 	return a.storage.saveState()
 }