Compare files (lists changes to turn old_file into new_file)

Compare files and directories.
More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

diff {{old_file}} {{new_file}}

click the source code to copy install diff on any operating system with command-not-found.com