Also, if you are using git, `git bisect` will do a great job at automating this kind of history search. It'll also do a nice binary search quickly narrowing down the culprit.

Additionally, you said "As luck would have it, it was a big one," - this is what I personally use `git add -p` and `git rebase -i` for before pushing to the public repo: I try to keep the commits as small and self-contained as possible such that finding the faulty commit gets much simpler, because there will be no "big one".