How Does Google Desktop Decide What’s A Text File?

So I finally broke down and installed Google Desktop even though it won’t index my web pages or email since I use Firefox and Thunderbird. I installed it because of the potential to index all of my source code because I am always thinking to myself “I just know I’ve got some source around here to do that…”

So I installed it yesterday, but what I want to know is how does the indexer decide what is a text file and what isn’t? It obviously isn’t just looking for files ending in .txt, but it does seem to have a list of extensions that it checks. I have installed the tool on two different machines, and after over 24 hours, I still have no indexing of any Ruby, Lisp or C# files. I can see plenty of results inside Java, C, Perl and Python files, which is why I think they have a list of “approved” text file extensions. I could be wrong and it just hasn’t gotten to any of my Ruby or Lisp files yet, but I’ve got tons of Ruby files on my system, so it seems like a slim chance that it wouldn’t have run across any of them. I’ll keep an eye on it, but I’m doubtful at this point.

I really hope this is just a time issue. I think this tool will be really useful (despite the email and browser issues) but it needs to find the files I care about.