The foundational piece of this project is the library which both the CLI and the GUI will consume, so it makes sense to start here. When designing the library--its inputs, outputs, and general behavior--it helps to understand what exactly do we want this system to do, so let's take some time to discuss the functional requirements.
As stated in the introduction, we'd like to be able to search for duplicate files in an arbitrary number of directories. We'd also like to be able to restrict the search and comparison to only certain files. If we don't specify a pattern to match, then we want to check every file.
The most important part is how to identify a match. There are, of course, a myriad of ways in which this can be ...
