TDB2

- Full implementation of TDB2::add, which includes pending/completed, undo
  and backlog.
- Removed obsolete TF2::commitUndo, which is no longer necessary.
- Added File::truncate method, to allow a TDB2 shortcut.

src/File.cpp

@@ -280,6 +280,16 @@ void File::append (const std::vector <std::string>& lines)
   }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+void File::truncate ()
+{
+  if (!fh)
+    open ();
+
+  if (fh)
+    ftruncate (h, 0);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 //  S_IFMT          0170000  type of file
 //         S_IFIFO  0010000  named pipe (fifo)