Is there a description of how the Espruino source in github is organized?

Personally I'd forget the GitHub search and use something on your PC instead. About the only thing it seems to work with is the issues list.

The actual file you need is pinutils.py. I think it's in the same directory so it really shouldn't have been too hard to find if search worked.

There's a bit of info about organisation - and what is in each directory - in the readme file. I'm open to additions though - I tend not to think what it would be like for newcomers now :)