Semi-automatic way to track changes in a latex file

calc_diff.sh

#!/usr/bin/env bash

# these can also be commandline args...
OLD_TEX=paper_orig.tex # previous draft, submission, etc.
NEW_TEX=paper.tex      # current working version

if [[ "$1" = 'clean' ]]; then
    rm -f diff*
else
    latexdiff $OLD_TEX $NEW_TEX > diff.tex
    latexmk -pdf diff.tex
    open diff.pdf
fi

Note that this requires latexdiff and latexmk.