Fix bug that empty log directories are created on any command with --help argument (#753)

internal/logfile/logfile.go

@@ -57,6 +57,10 @@
 
 // Initialize is invoked as part of command execution to create log file just before it's needed.
 func Initialize(ctx *kingpin.ParseContext) error {
+	if *logDir == "" {
+		return nil
+	}
+
 	now := clock.Now()
 
 	suffix := "unknown"