Give me a repo and I'll tell you what languages it was written with.
var gitLang = require("github-languages");
gitLang("https://github.com/mcwhittemore/github-language", function(err, langs){
console.log(langs);
});
// ==> {'JavaScript':100.0}
https://github.com/mcwhittemore/github-language
git@github.com:mcwhittemore/github-language.git