latexdiff and \let

Question

I added this line to my document to redefine l@chapter later:

\let\oldlchapter\l@chapter

Now latexdiff creates this, which doesn't compile:

\let\oldlchapter\DIFadd{\l@chapter
}

What can I do to fix this?

Answer 1

First of all, latexdiff is designed to work with LaTeX document syntax, not raw TeX commands such as \let. In this case, a small change to latexdiff leads to the correct behaviour (see below - this has been implemented in the development version of latexdiff on GitHub and will be contained in versions 1.2.1 up (not yet released as of January 3, 2017).

More generally, use environment \DIFnomarkup (which you need to define to do nothing) to protect TeX commands from processing by latexdiff. see latexdiff manual or man pages for a more detailed explanation.

Required change to latexdiff:

Find the line:

  my $cmdoptseq='\\\\[\w\d\*]+'.$extraspace.'(?:(?:<'.$abrat0.'>|\['.$brat0.'\]|\{'. $pat_n . '\}|\(' . $coords .'\))'.$extraspace.')*';

and add one @ character such that it reads:

  my $cmdoptseq='\\\\[\w\d@\*]+'.$extraspace.'(?:(?:<'.$abrat0.'>|\['.$brat0.'\]|\{'. $pat_n . '\}|\(' . $coords .'\))'.$extraspace.')*';