Detection of duplicate files isn't that simple; refer
a similar thread. If that's not what you intend, a bit more explanation is needed.
The romantic image of an über-programmer is someone who fires up Emacs, types like a machine gun, and delivers a flawless final product from scratch. A more accurate image would be someone who stares quietly into space for a few minutes and then says “Hmm. I think I’ve seen something like this before.” - John D