Add logging and update validation

toolflow/src/main/scala/com/minres/tgc/hammer/Main.scala

@@ -11,7 +11,7 @@ object Main {
   var conf: HammerConf = uninitialized
 
   def main(args: Array[String]): Unit = {
-    var logger = Logger("TGCHammer")
+    val logger = Logger("TGCHammer")
     conf = new HammerConf(args.toIndexedSeq)
 
     val logLevel = conf.verbose() match {
@@ -22,14 +22,23 @@ object Main {
     }
     LoggerFactory.getLogger(org.slf4j.Logger.ROOT_LOGGER_NAME).asInstanceOf[ch.qos.logback.classic.Logger].setLevel(logLevel)
 
-    os.makeDir(Global.OUT_DIR)
-    os.makeDir(Global.TMP_DIR)
+    logger.trace(s"Creating output directory ${Global.OUT_DIR}")
+    if (conf.emptyOutputDir()) os.remove.all(Global.OUT_DIR)
+    os.makeDir.all(Global.OUT_DIR)
+    logger.trace(s"Creating temp directory ${Global.TMP_DIR}")
+    os.makeDir.all(Global.TMP_DIR)
     conf.subcommand match {
       case Some(c: MySubcommand) =>
+        logger.info(s"Executing subcommand ${c.name}")
         val tasks = c.getRequiredTasks
+        logger.debug(s"Subcommand requires ${tasks.size} tasks")
+        logger.info(s"Validating tasks")
         tasks.foreach(_.validate())
+        logger.info(s"Executing tasks")
         tasks.foreach(_.execute())
       case _ =>
+        logger.error(s"Found no subcommand, see help below")
+        conf.printHelp()
     }
   }
 }