Google has a giant monolithic code repo with over 2 billion lines of code. It's really amazing.
> Most of Google’s code is stored in a single unified source-code repository, and is accessible to all software engineers at Google . There are some notable exceptions, particularly the two large open-source projects Chrome and Android, which use separate open-source repositories, and some high-value or security-critical pieces of code for which read access is locked down more tightly. But most Google projects share the same repository. As of January 2015, this 86 terabyte repository contained a billion files, including over 9 million source code files containing a total of 2 billion lines of source code , with a history of 35 million commits and a change rate of 40 thousand commits per work day .
Probably they just delete the directory or whatever, but it's still inside the VCS history.