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git-latexdiff errors? Workaround: using latexdiff manually allows fixing broken things

December 4, 2017 Leave a comment

In a previous post we have highlighted git-latexdiff, which visually highlights the changes between two versions of the same latex file managed with git – without you being required to checkout any versions of that file yourself. In certain cases git-latexdiff might terminate with errors instead of producing a visual diff file. For example, it might struggle with broken latex code, broken figures, certain usage of subfiles, etc. In such cases, it might help to manually do what git-latexdiff would do fully automatically for you. Here’s a simple step-by-step explanation of how you could achieve visual highlighting even with broken Latex files:

  • Have the repository R2 available, which contains the file F in the newer version you want compared. Copy the repository R2 to a different folder R1 (you could do this on other ways too, but with copying you can hardly mess things up). In the copied folder checkout the version of the repository which contains F in the older version you want compared. Therefore, R2 contains F in the new version and R1 contains F in the old version now.
  • You can now fix both versions of F  should they contain broken latex code. F essentially needs to compile in both R2 and R1.
  • If you run into troubles with figures (also in subsequent steps) it might be helpfull to add the “draft” parameter to the documentclass. This can be done in both F files or in the diff.tex generated later. It disables figures in the documents, which causes less problems later in case figures are part of what prevents latexdiff, pdflatex, or one of the other tex tools from doing their jobs. This might also the case if figures have both been added and removed, or if figure paths have changed between those versions.

After those preparations, in your terminal run the following command from somewhere outside both repositories:

latexdiff --append-safecmd=subfile R1/path/to/F R2/path/to/F --flatten > diff.tex

The option

--apend-safecmd=subfile

makes the subfile command safe to use within the scope of the “\DIFadd” or “\DIFdel” commands, which latexdiff uses to mark differences between versions. The option

--flatten

replaces “\input” and “\include” commands within body by the content of the files in their argument. This makes all content of the document appear in your highlighted diff in the end. If the latexdiff-command succesfully generated a diff.tex file, copy this file into R2 or R1, right next to where F is located. You should now be able to compile and show the pdf file:

pdflatex diff.tex && biber diff && pdflatex diff.tex && evince diff.pdf

Fixing even more problems

In case you run into errors during compilation using the method above you might be able to manipulate the diff.tex file. If this does not help and if you are just interested in differences in the plain text there is an even stronger workaround you can try: you can copy the important parts of the content of your main .tex files in both R1 and R2 into newly created – and therefore clean – dummy.tex files. The important part of the text will usually be textual paragraphs, and more importantly for big documents, includes of subfiles. The dummy.tex files need to be of the same document class (e.g. a book class document will need a clean book again to work).  Remember to do this in an identical way in both R1 and R2. Afterwards you can compare the dummy.tex files using latexdiff (instead of the original main files). Doing so can circumvent many different types of problems that might be introduced due to code in custom Latex .cls or .sty files that is either unsupported by latexdiff and/or is broken in some way.

git latexdiff usage: visually highlight changes in version controlled Latex files

October 2, 2017 1 comment

This is a follow-up post to latexdiff-git, which is outdated by now.

latexdiff is a powerful tool that uses two Latex files to generate a third Latex file in which differences between the first two files are visually highlighted. latexdiff is especially useful when comparing an old with a new version of the same Latex file. However, latexdiff does not account for any version control on its own. This means that if you want to visually highlight the differences between two versions of a version controlled Latex file, you are required to manually checkout the two different versions ahead of comparing them with latexdiff. In case you are using git as your version control system, this is where git-latexdiff comes into play. It accounts for checking out the different version of a Latex file as well as comparing them with latexdiff in a single command: you only need to specify which latex file and versions should be used for the comparison.

Preconditions

Ensure you have git, a latex distribution (e.g. texlive-full), and latexdiff installed and available in the path of your CLI.

git-latexdiff installation

Clone git-latexdiff:

git clone https://gitlab.com/git-latexdiff/git-latexdiff#

Follow instructions in the README. This will involve a:

sudo make install

in most cases on an Ubuntu system. If all went well “git latexdiff” should be available in your CLI (it should print the help message):

user@machine:~$ git latexdiff

fatal: Please, provide at least one revision to diff with.
Usage: git latexdiff [options] OLD [NEW]
 git latexdiff [options] OLD --
 git latexdiff [options] -- OLD
Call latexdiff on two Git revisions of a file.

OLD and NEW are Git revision identifiers. NEW defaults to HEAD.
If "--" is used for NEW, then diff against the working directory.

Options:
 --help this help message
 --help-examples show examples of usage
 --main <file> name of the main LaTeX, R Sweave,
 or Emacs Org mode file.
 The search for the only file containing 'documentclass'
 will be attempted, if not specified.
 For non-LaTeX files, a reasonable `prepare` command
 will be used unless explicitly provided
 --no-view don't display the resulting PDF file
 --latex run latex instead of pdflatex
 --bibtex, -b run bibtex as well as latex
 (pdflatex,bibtex,pdflatex,pdflatex)
 --biber run BibLaTex-Biber as well as latex
 (pdflatex,bibtex,pdflatex,pdflatex)
 --view view the resulting PDF file
 (default if -o is not used)
 --pdf-viewer <cmd> use <cmd> to view the PDF file (default: $PDFVIEWER)
 --no-cleanup don't cleanup temp dir after running
 --no-flatten don't call latexpand to flatten the document
 --cleanup MODE Cleanup temporary files according to MODE:

- keeppdf (default): keep only the
 generated PDF file

- none: keep all temporary files
 (may eat your diskspace)

- all: erase all generated files.
 Problematic with --view when the
 viewer is e.g. evince, and doesn't
 like when the file being viewed is
 deleted.

--latexmk use latexmk
 --latexopt pass additional options to latex (e.g. -shell-escape)
 -o <file>, --output <file>
 copy resulting PDF into <file> (usually ending with .pdf)
 Implies "--cleanup all"
 --tmpdirprefix where temporary directory will be created (default: /tmp).
 Relative path will use repository root as a base
 --verbose, -v give more verbose output
 --quiet redirect output from subprocesses to log files
 --prepare <cmd> run <cmd> before latexdiff (e.g. run make to generate
 included files)
 --ln-untracked symlink uncommited files from the working directory
 --version show git-latexdiff version.
 --subtree checkout the tree at and below the main file
 (enabled by default, disable with --whole-tree)
 --whole-tree checkout the whole tree (contrast with --subtree)
 --ignore-latex-errors keep on going even if latex gives errors, so long as
 a PDF file is produced
 --ignore-makefile ignore the Makefile, build as though it doesn't exist
 -* other options are passed directly to latexdiff
 --bbl shortcut to flatten a bbl file of the same name as the project
 --latexpand OPT pass option OPT to latexpand. Use multiple times like
 --latexpand OPT1 --latexpand OPT2 to pass multiple options.
 --latexdiff-flatten use --flatten from latexdiff instead of latexpand

Unrecognized options are passed unmodified to latexdiff.

git-latexdiff usage

The main CLI usage of git-latexdiff is:

git latexdiff --main YOURFILE OLD_HASH [NEW_HASH]

A bunch of useful options are available for git-latexdiff. For example:

-v # good in case you run into any errors
--cleanup keeppdf # delete the checked-out 'old' and 'new' folders but keep the pdf
--cleanup all # delete all generated files afterwards
--output FILE # copy pdf before deleting it to FILE (disables automatically viewing the pdf). good in combination with --cleanup all
--tmpdirprefix ./FOLDERNAME/ # alternative to the above: specify where temporary stuff is stored, makes it easier to access diff files. good in combination with --cleanup keeppdf
--bibtex # also run bibtex
--biber # also run biber

Therefore, the command you might want to run therefore might be similar to this:

git latexdiff --main MYFILE.tex --bibtex --output git-latexdiff.pdf --cleanup all OLD_HASH NEW_HASH

…where you can specify

--

as NEW_HASH, if you want to run git latexdiff against the current (possibly unstaged/uncommited) version of the file, or where you can leave out NEW_HASH completely, if you want to run it against the last commit. Or your command might look similar to this:

mkdir git-latexdiff; git latexdiff --main MYFILE.tex --tmpdirprefix ./git-latexdiff/ --cleanup keeppdf OLD_HASH