Word-by-word diffs in Git

I personally like all my LaTeX files wrapped at about 80 columns, with rare exceptions. Of course, I track them all with Git. I use Vim, so it’s really easy to rewrap a paragraph whenever I add or delete content from it. The sad thing is, it totally screws up my diffs!

Have you ever tried looking at the history for any page in Wikipedia? It’s beautiful, intuitive, and word-centered. Forget about lines, they’re not suitable for text. Words, however, are.

Example of the word-by-word diff in Wikipedia

Well, version control systems use the line-by-line diffs, which don’t really help when comparing two versions of a text file. What to do now?

I have googled a bit, and found about wdiff. Seemed interesting, but the output was really ugly. I first thought of using it as an external diff tool in git, but gave up. Nice to know it exists, though.

Then, for some reason, I decided to read the git-diff help one more time and, to my surprise, the feature we want is already there! Introducing to you… git diff --color-words!

Sample output of git diff --color-words

Amazing, right? Notice how deleted words are in red, added words in green, and the unchanged text surrounding it in white (or black, if you’re not into dark backgrounds). Much more natural and easier to spot differences than the original git diff! But you should be asking yourself “Am I going to have to write this long command every time?”. Certainly not! Git allows you to create aliases, which I just learned about. You can create an alias named wdiff, and the result is a new command, git wdiff, that perfectly fits our needs! Great, isn’t it?

Here’s two ways to do it:

• Via command-line: git config --global alias.wdiff diff --color-words; or
• Editing your ~/.gitconfig, add the following lines:
  [alias]
    wdiff = diff --color-words


Piece of cake, right? Hope you liked it, and happy word-diffing!

Special thanks to my friend Carlos Eduardo, who helped me find a good way to illustrate the word-by-word diff!

Update: Better tokenization for LaTeX files

It seems that Git 1.6.2 and earlier now support the use of a regular expression to define what is a word for --color-words. Also, the manpage for the .gitattributes file shows that some filetypes already have useful built-in configurations, including the regular expressions in question, and LaTeX is one of those formats.

In practical terms, this means that \section{Title} can now be seen as several tokens instead of a single word, so renaming the section will provide you with a smarter highlighting.

So, if you don’t have a .gitattributes file yet, you should create one. I just found out about them, and it’s pretty cool. It adds other interesting functionalities such as hints on the diffs for which point in the file (for instance, the LaTeX chapter/(sub)section name) those diffs are taking place. The manpages can tell you more about it, so I’ll keep it short. It’s very easy to enable this, just add the following line to a .gitattributes file in your repository (its syntax is very similar to .gitignore) and everything is set for you:

*.tex    diff=tex

Even if your version is older than 1.6.2, the other benefits are much probably available for you and are well worth it, so give it a try anyway!

About these ads