Thanks for helping. Your test was what I expected to happen, but the left side of my project window (the files in the project) did not show any question marks, etc. I did not find any contextual menu choice for adding files in the project to the new repository. I figured Xcode just doesn't provide a way to add source code control to an existing project. Which I thought I should ask about here, because this is basic functionality that might be missing -- unless I'm missing something. The workaround I used: starting a fresh new Xcode project with a Git Repository checkbox on, and I migrated all my project files to that new project. Case closed.