Add get command

Change-Id: Id06539070fb8d815786149e1479e93d75d4b70f1
diff --git a/src/ast_handlers.hpp b/src/ast_handlers.hpp
index bddc83e..686ae30 100644
--- a/src/ast_handlers.hpp
+++ b/src/ast_handlers.hpp
@@ -394,6 +394,8 @@
 
 struct commit_class;
 
+struct get_class;
+
 struct command_class {
     template <typename Iterator, typename Exception, typename Context>
     x3::error_handler_result on_error(Iterator&, Iterator const&, Exception const& x, Context const& context)