Diff. Patch. Change. Delta. Δ. Whatever you call it, diffs are pretty much the aggregate output of any developer’s day. A bunch of deletions and additions from a set of files that can be codified in a .patch file as a bunch of pluses, minuses and context indicators. ‐‐‐ a/todo.md +++ b/todo.md @@ -1,5 +1,4 @@ # TODO buy anniversary present build arduino-based vaucanson’s duck -blog on git diffs fork webkit ‐‐ I’m still undecided as to whether it’s depressing or amazing that our life’s work can be so simply encoded. Regardless, git has given us a bunch of neat ways at looking at these diffs. The following post is a quick primer on the various incantations of git diff. Note that I’m going to be focusing on different output format for viewing diffs. There’s also a whole range of ways you can specify different commits and paths to diff, but that’s a topic for another day. git diff You’re probably already familiar with the built in git diff command. By default, diff will show you the difference between unstaged changes to currently tracked files, and your current HEAD. For example: $ cat 2cities.txt It was the best of times, it was the blurst of times. $ sed -i ‘.tmp’ ‘s/blurst/worst/’ 2cities.txt $ git diff It was the best of times, -it was the blurst of times. +it was the worst of times. This works fine, but it’s unfortunate that it shows up as one removed line followed by one added line. All I did was change one word! git diff ‐‐color-words git diff also has a special mode for highlighting changes with much better granularity: ‐‐color-words. This mode tokenizes added and removed lines by whitespace and then diffs those. $ git diff ‐‐color-words It was the best of times, it was the blurstworst of times. That’s an improvement! Now we’re down to the individual words that have changed. But if you look closely, we’ve really only changed three characters: “blu” has become “wo”. We can do even better. git diff-highlight If you clone the git source you’ll find a sub-directory called contrib. It contains a bunch of git-related tools and other interesting bits and pieces that haven’t yet been promoted to git core. One of these is a perl script called diff-highlight. diff-highlight pairs up matching lines of diff output and highlights sub-word fragments that have changed. $ git diff | ~/src/git/contrib/diff-hightlight/diff-highlight It was the best of times, -it was the blurst of times. +it was the worst of times. Sweet! Now we’ve pared down our diff to the smallest possible change. If you like this fine-grain way of looking at diffs, you can add a shell function alias to ~/.git/config to handle the piping to diff-highlight for you: 123[alias] # assumes git.git clone at ~/src/git diff-highlight = "!f() { git diff \"$@\" | ~/src/git/contrib/diff-highlight/diff-highlight; }; f" Then, you can get a nicely highlighted diff by simply invoking git diff-highlight. Diffing binary files If you make changes to a [...]
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