> I have to say that I used local search instead of trying to find something on the mozilla-central website.

On the contrary, I find searchfox to be the best code navigation tool I used. It has nice cross-language navigation features (like jumping from .webidl interface definition to c++ implementation), it has always-on blame (with more features too) and despite that it's really fast and feels extremely lightweight compared to GitHub interface. I really wish I had this with more projects, and I'll be sad if it ever dies.