Of course you don't just check the diff. Rather in your CI infra, it's important as part of every PR, it needs to be given the full repo to check if it introduces any issues. This works wonderfully on github, even with non SOTA tools like gemini-code-assist.

why do you think it's not possible to have full context of codebase? modern harnesses excel at finding all the right codepaths, even in a large codebase.