Keyboard shortcut for "Close all files" OR warn when closing a Project

When switching between branches, I always have existing files opened and want to quickly close them all but not the project.   

I often just use the keyboard shortcut Command W to quickly do that because "Close All Files" does not have a shortcut.  But my overzealous finger will obviously end up closing the Project itself.  

So either provide a keyboard shortcut for the former or a warning dialog for the latter.