Two projects with the same code base

Is it possible to have two projects in Xcode using the same code base?

I have an application that offers a demo version and a full version. They both have the same code, and I just set the flag in my plist file, and somewhere in my code I do

if (demo_mode) {
    // ...
} else {
    // ...
}

This is easy to test, but not suitable for the app store, as they require several different app icons and app names.

I could also make a copy of the project, but then I would have to apply the changes in one project to another (corrections, user interface changes, etc.). Therefore, I want to use the same source folder for two projects.