Determine changes between different versions of a LaTeX file (the resulting LaTeX file can be compiled to show differences underlined)

Determine differences between two LaTeX files.
More information: <https://ctan.org/pkg/latexdiff>.
Trick copyright: tl;dr; <https://github.com/tldr-pages/tldr>

latexdiff {{old.tex}} {{new.tex}} > {{diff.tex}}

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