Where can I find Google API JavaScript Library source code repository?

I've opened Google APIs Client Library for browser JavaScript, aka gapi just to find out that

Note: This repo does not contain the source code for the gapi client.

Where can I find a repository for gapi aka Google APIs Client Library for browser JavaScript. I know I can get it from https://apis.google.com/js/api.js. But I need a repo, I want to learn it, and examine it, and debug it.