The -G option used with git log will look for differences in the patches that contain added or deleted lines that match the given string. However, these lines could also have been added or removed because of some other refactoring/renaming of a variable or method. There is another option that can be used with git log, namely -S, which will look through the difference in the patch text in a similar way to the -G option, but will only match commits where there is a change in the number of occurrences of the specified string—that is, a line added or removed, but not added and removed.
Let's see the output of the -S option:
$ git log -S"isOutdated" --oneline f32b861 JGit 3.0: move internal classes into an internal subpackage ...
