How to find a commit that introduces (not removes) a string?

Hi all,

I know about git log's -S / -G, but I'm unable to make these search through *introduced* strings only. Is there a way to do so?

Thanks!

PS: I also read [1], but although the author claims to be interested in introduced strings only, he seems to be satisfied with -G, which slightly puzzles me.

[1] http://stackoverflow.com/questions/5816134/git-finding-a-commit-that-introduced-a-string