On top of what others have already flagged this is a big no for any companies security & compliance. Why would any company share their private codebase ?
Great question; security and compliance is a very big consideration for our customers. All code review on PullRequest is done within the platform, engineers in the PullRequest network cannot clone branches like in a garden variety source control, and we have a number of tools to give clients as much control as possible as to what our platform and engineers in our network are exposed to (e.g., https://docs.pullrequest.com/pullrequest-docs/code-review-se...).
We work very closely with our customers to ensure configurations are set up to provide our engineers with adequate context while limiting or outright restricting exposure of things they want private private.
This is also a big part of why PullRequest Reviewers are by and large restricted to US-based engineers. This ensures accuracy and consistency of criminal background checks and ease of enforceability for our non-disclosure agreements. From a legal risk assessment perspective, using PullRequest is similar to hiring a technical consultant.