Hey Chris,
If you set up your application as a project, and use MATLAB's Source Control to share your project to Git, you are able to inspect the differences within MATLAB, which probably is the correct way to do what you want to do.
Optional info below:
If you unzip the file, under 'matlab' folder, there's a file called 'document.xml' which contains the script you see in App Designer, however, you can only use it to see the changes, but you cannot reuse the file, as it is not yet known to us how to change data inside and have a working application.
