I recently started using Tim Pope's git-vim plugin. The first time I used :Gstatus and added a file with one keystroke had me won over. Pure genius if you ask me!
1. git blame
2. move to the blame window and hit 'o' to open the commit
3. discover that the line in question was merely moved not created by this commit, then move to the --- line in the diff and hit 'o' to open the previous version of the file.
4. repeat from step 1
It's a few more steps than `git log -S` but it provides a different kind of flexibility. You can trace all manner of historic code migrations even without a common search term.