Very relatable. I still recall when our team at Microsoft, about 20 years ago, had a dedicated "build engineer" who would be given the task to create a new branch for the product. He would disappear for a few days and re-emerge with the announcement that a new branch had been officially created and was ready to be used. Hard to imagine that in git world.

When I went back to Perforce I was reminded of why that was a thing. You're making a full copy of everything. They recently introduced a virtual copy stream, but I remember people advising against using it, for reasons I can no longer remember. It seemed like a potentially sensible approach.

Oh, and thanks for writing Game Programming Patterns. That was a great resource.