This works pretty good too, does not suffer from the github blocking of your script and is probably even easier.
Github might include something like a warning on your repo that it includes possible data that you might not want out there.
https://github.com/search/advanced
You can access all of this functionality with ghrabber.
One of my suggestions to Github is that they disable indexing of dotfiles of all persuasions (including contents of dot-directories), unless the repo owner explicitly opts in. That would make it much harder to find a very large fraction of the more obvious leaks.
If true, doesn't this make crippling the usefulness of GH's search really superfluous?
Full disclosure: I'm never a fan of crippling search to cover the ass of someone who has pushed sensitive information to a publicly accessible location. I'm still sore about Google's decision to do things like prevent one from searching for -for instance- credit card numbers. :(