I think Marx is rolling in his grave over the tirelessly expended human to recreate what almost definitely already exists on a floppy sitting in some “IP - Do Not Touch” lock box. But maybe endless puzzles for ever cleverer people is the point of it all.
I dunno. I was a gamedev. I'm pretty sure everything got thrown out. I don't remember ever taking any source home. It was all managed through Visual Source Safe (!) on a local server.
The 80s games were mostly coded in bedrooms, but after that it all moved to teams in offices and a lot of studios went boom-to-bust pretty quickly.