Pros

• Single lint, build, test and release process.
• Easy to coordinate changes across modules.
• Single place to report issues.
• Easier to setup a development environment.
• Tests across modules are run together which finds bugs that touch multiple modules easier.

Cons

• Codebase looks more intimidating.
• Repo is bigger in size.

Google

The vast majority of Google's software assets continues to be stored in a single, shared repository. See Why Google Stores Billions of Lines of Code in a Single Repository - The Google proprietary system that was built to store, version, and vend this codebase is code-named Piper. Google practices trunk-based development on top of the Piper source repository. The vast majority of Piper users work at the head

Symphony Blackfire

• https://speakerdeck.com/fabpot/a-monorepo-vs-manyrepos

Javascript

monorepo

• https://github.com/facebook/react/tree/master/packages
• https://github.com/meteor/meteor/tree/devel/packages
• https://github.com/emberjs/ember.js/tree/master/packages

Sync to standalone repo

• submodule
• old git subtree split command:
  • splitsh automatically synchronize a monolithic repository to standalone repositories in real-time (old)