Just reading out of my notes, the only non-highlighting detector I was looking at was https://github.com/blakeembrey/node-language-detect, but it's not widely used or developed as far as i can tell.

If you have Ruby in your stack, it's easy -- use github's own https://github.com/github/linguist

You might also be able to use just the language definition files from https://github.com/syntaxhighlighter