What does git diff –word-diff do and when might it be useful?

git diff --word-diff is a powerful command in Git’s version control system that provides a more granular level of difference-checking than the traditional git diff. To fully understand its utility, we first need to understand what git diff does in a normal scenario.

The git diff command is used in Git to show changes between commits, commit and working tree, etc. By default, git diff highlights the entire line that has been changed. This line-level granularity can be great for many changes, but in cases where only a single word or a few characters have been changed, it can be somewhat overkill. It might be harder to quickly identify what exactly has been changed within that line, especially if it’s a long one.

That’s where git diff --word-diff comes in. Instead of highlighting the entire line that contains changes, git diff --word-diff highlights the exact words that were changed. It breaks down the differences to the word level. This means that you’ll see exactly which words were added, removed, or changed, making it easier to understand small changes within lines.

The format of the output is:

  • Deletions are shown in red and marked with a -.
  • Additions are shown in green and marked with a +.

For instance, if you have a sentence in a text file like:

The quick brown fox jumps over the lazy dog.

and you change it to:

The quick brown fox jumps over the lazy cat.

If you use git diff, it will show that the entire line has been changed. However, if you use git diff --word-diff, it will show you that only the word “dog” was changed to “cat”.

So, when might it be useful?

  • Long lines of text/code: The command is particularly useful when you’re dealing with long lines of text or code and want to quickly spot what has been altered within those lines.
  • Documentation: When revising documentation, changes are often word-level rather than line-level, so git diff --word-diff is perfect for these situations.
  • Code reviews: It can help when reviewing code, as it allows reviewers to see exactly what has been changed without the noise of whole line changes.
  • Small tweaks: When you’re making small tweaks to your code, git diff --word-diff helps you review your changes before you commit them.

Remember, git diff --word-diff doesn’t alter the way Git tracks changes – it only affects the way changes are displayed to you. Git still works on a line-level granularity when it comes to tracking changes. This command only alters how you view these changes.