I've written some stuff but nothing that is widely used.
I've upstreamed in a lot of repos of some bigger projects.
I honestly don't know how these guys do it.
Even on a day where I finish early, I'm tired and would barely be able to get a few lines out.
But some of these project the guys are committing tons of code every day.
One example I recently upstreamed on was
Marlin.
Just lots of lines of code every day.
My assumption is the guy actually does it as his day job.
There is no way someone can get that much code out and still maintain a day job (even a lax day job)