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git-difftool: an easy way to highlight changes in git-managed text files

In two previous posts (post one, post two) we have shown how to use git latexdiff and latexdiff to visually highlight the differences of a Latex file in between its different versions in the form of a Latex-compiled diff file. For comparing arbitrary textfiles instead of Latex files, no Latex-based visual comparison is available. However, git itself ships a nice little tool to compare two different versions of the same textfile and highlight its differences: git difftool. It basically does two things for you:

  • Checkout the versions of the file to compare
  • Fire up your diff program to show you/highlight the differences

All you need to do is specify the file and the versions you want to compare.

Configuration

git_icon

git difftool is part of the git installation. However, it needs to know which diff program you want to use when calling git difftool. You can specify this by adding the following snippet to your ~/.gitconfig:

[diff]
    tool = MY-DIFF-TOOL

where MY-DIFF-TOOL could be vimdiff, kdiff3, or similar (ensure the tool you specify is installed and available in the PATH on your machine). Now git difftool should be ready for usage:

user@machine:~$ git difftool -h
usage: git difftool [-t|--tool=] [--tool-help]
                    [-x|--extcmd=]
                    [-g|--gui] [--no-gui]
                    [--prompt] [-y|--no-prompt]
                    [-d|--dir-diff]
                    ['git diff' options]

Usage

git difftool has a simple call syntax (in fact the same as git diff). The command you might want to compare files might be similar to this:

git difftool COMMIT1 COMMIT2 FILE

If you use

--

as COMMIT1 and leave out COMMIT2 you will see the differences between the file in its current, possibly unstaged/uncommited stage and its last commit. If you specify a hash for COMMIT1 and use

--

as COMMIT2 you will see the differences of the current file to the specified commit instead. If you specify hashes for both COMMIT1 and COMMIT2 you will see the differences between those two versions of the file.

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

October 2, 2017 2 comments

This is a follow-up post to latexdiff-git, which is outdated by now.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