* Predefined explicit requirements (a tight spec).
* No distractions.
* No colleagues (i.e. you're working on a non-blocking single thread of execution).
* Enthusiasm.
* An unhealthy enjoyment of coding.
I have worked at this pace and I'm sure many others have, but you need to have those pre-requisites (and they are RARE!).
Bare in mind that if you're the only developer those commits probably haven't been tested and you're not worrying about damaging other people's code.
Of course, you can't scale that model :-)
Which btw is a fantastic real world analogy of why multi-threading can suck horrifically in some cases and why that parallel execution isn't always a good thing.
NOTE: None of that takes a way from a totally awesome and fearless project to take on and complete (which I believe it is?).