sure! it used a collection of tools, the main ones were

* copybara [https://github.com/google/copybara] to mirror between github and our internal repo and transform the source tree layout to our internal conventions

* mercurial patch queues [https://hgbook.red-bean.com/read/managing-change-with-mercur...] to apply internal changes

there are internal tools to automate the copybara configuration for python packages specifically, and to map between mercurial and google's version control system, but that's the main idea, and a specific review process for adding new packages.

the process is actually documented here though not all the referenced tools are available (or even applicable) externally: https://opensource.google/documentation/reference/thirdparty...