Well, as your're looking for a tool why not just use a Kompare. Its very powerful and well known which is used by most developers who uses Linux.
https://www.kde.org/applications/development/kompare/https://docs.kde.org/trunk5/en/kdesdk/kompare/using.html
Kompare is a GUI front-end program that enables differences between source files to be viewed and merged. It can be used to compare differences on files or the contents of folders, and it supports a variety of diff formats and provide many options to customize the information level displayed.