How to search for strings in Git commit additions or deletions

You've probably run into this problem a few times: you're working on a feature and discover a code section that doesn't make sense to you. There's no context, no comments, no help — it's just you and these mysterious lines staring right back at you.

// when was this added? 👇
if (someVar === 1.32) {
  // ...
}

You try to use git blame to learn more about the mysterious code, but recently applied code style changes and refactorings hide the commit when these lines have entered the code base. Looking at the file history isn't of great help either because the code base is old, and this particular file is very busy.

Today I learned that the Git log command includes a -S flag to help with this exact problem.

# search for a string in file additions or deletions
git log -S 'if (someVar === 1.32)'
commit 08f579675fc62c63cd182b580dc80fac53b02526
Author: stefan judis <stefanjudis@gmail.com>
Date:   Sun Nov 28 20:06:04 2021 +0100

  developing a mysterious feature

-S scans all commit additions and deletions, looking for your defined substring. So, if you're looking for a weird-looking variable or unique condition, you'll find the commit that added it quickly. git log -S is pretty neat!

Big thanks go to Alex Harri, who shared the flag and some more advanced Git -S combinations:

# start with the oldest commits first
git log -S "YOUR STRING" --reverse

# only show commit hash and message
git log -S "YOUR STRING" --oneline

Happy commit searching!