StateDMI / Development Environment / KDiff3
KDiff3 software is highly useful for comparing source files and folders of files.
Install the appropriate version of the software for the operating system from the download page on the following page:
KDiff3 can be used directly or can be configured within git
to use for the "difftool".
StateDMI's CompareFiles
command also provides an option to use KDiff3 to visually compare files.