Searching code with Sourcegraph

Not sure if it qualifies as "relatively recent", but the earliest tool for structural search (and refactoring) I'm aware of is James Gosling's Jackpot circa 2000 (it now lives on as part of NetBeans IDE). Linux developers should also be familiar with Coccinelle, so-called "semantic search" tool used to find and fix bugs automatically, and also for widespread refactorings. There's also my favourite feature of Intellij IDEA :) I'm kind of a connoisseur of static analysis and structural search/replace tools so it's good to see another one out there!