How do I get SemanticMerge to recognize C++?

Question

According to the documentation Semanticmerge supports C++ natively.

But when I run it on a set of files (from TortoiseHg), despite the fact that they have a .cpp extension, it thinks they are C#. This of course messes up the language parsing and completely negates the whole point of the tool!

I can't see any settings for file associations, or a manual override for the current merge.

Answer 1

Lunch the SemanticMergeTool.exe with -l=cpp switch
For a complete set of options run SemanticMergeTool.exe -?