ian c. anderson

Code Sleuthing With Git

Consider this scenario:

  • You want to delete a method foo that seems to be no longer used.
  • You’re a bit nervous because you work in a dynamic language (like Ruby), so you can’t rely on grep to find all usages of this method.
  • You wonder, why did this method ever exist?
  • git blame isn’t very helpful - just shows the last change to that method, which isn’t relevant

git log -S to the rescue

    $ git log -S foo

    commit 8f19a1fa0...
    Author: Ian C. Anderson
    Date:   Thu Mar 6 21:44:17 2014 -0500

        stop using the foo method because eww

    commit 216895189...
    Author: Ian C. Anderson
    Date:   Thu Mar 6 21:09:44 1999 -0500

        new foo method - so great!

From the git-log docs:

-S <string> Look for differences that change the number of occurrences of the specified string (i.e. addition/deletion) in a file.

So git will spit out all of the commits that either deleted or added the given string (e.g. calls to a method)

Even more powerful: git log -G

-G<regex> Look for differences whose patch text contains added/removed lines that match <regex>.

These two commands have become indispensable tools for me, especially when navigating an old codebase with a lot of crufty code.