This just started happening today out of nowhere. Instead of only the project I’m working on appearing in Source Control, every project inside my Xcode projects folder is now showing up in the Source Control navigator. This is happening in both the Changes and Repositories tabs.
Git repos can be big source of this problem. But there's one more to check.
Xcode projects actually consist of two parts - the project and the workspace. The source code integrations are based on the workspace. Xcode uses a shared workspace by default. But you can create a dedicated workspace file for your project and then just open that file instead of the project file.