diff --git a/src/fileio_func.h b/src/fileio_func.h
--- a/src/fileio_func.h
+++ b/src/fileio_func.h
@@ -12,6 +12,7 @@
 #ifndef FILEIO_FUNC_H
 #define FILEIO_FUNC_H
 
+#include "core/enum_type.hpp"
 #include "fileio_type.h"
 
 void FioSeekTo(size_t pos, int mode);
@@ -92,12 +93,24 @@ public:
 class TarScanner : FileScanner {
 	uint DoScan(Subdirectory sd);
 public:
+	/** The mode of tar scanning. */
+	enum Mode {
+		NONE     = 0,      ///< Scan nothing.
+		BASESET  = 1 << 0, ///< Scan for base sets.
+		NEWGRF   = 1 << 1, ///< Scan for non-base sets.
+		AI       = 1 << 2, ///< Scan for AIs and its libraries.
+		SCENARIO = 1 << 3, ///< Scan for scenarios and heightmaps.
+		ALL      = BASESET | NEWGRF | AI | SCENARIO ///< Scan for everything.
+	};
+
 	/* virtual */ bool AddFile(const char *filename, size_t basepath_length, const char *tar_filename = NULL);
 
 	/** Do the scan for Tars. */
-	static uint DoScan();
+	static uint DoScan(TarScanner::Mode mode);
 };
 
+DECLARE_ENUM_AS_BIT_SET(TarScanner::Mode)
+
 /* Implementation of opendir/readdir/closedir for Windows */
 #if defined(WIN32)
 #include <windows.h>