@sindresorhus Greptile AI does that: https://www.greptile.com/

As a new developer, I used it to understand a large open-source codebase that was too big for other AI chats. Greptile answered my basic questions which led to a successful PR for a bug fix.

But for my personal (small) SwiftUI projects, I prefer ChatGPT and Claude AI. It's easier to just drag and drop my latest files from Xcode's Project navigator to keep those chats updated. Greptile seems to be most useful with large projects.