I was never a fan of hg either, but now I can use jj, and get some of those benefits without actually using it directly.
Fun story: I don't really know what Microsoft's server-side infra looked like when they migrated the OS repo to git (which, contrary to the name, contains more than just stuff related to the Windows OS), but after a few years they started to hit some object scaling limitations where the easiest solution was to just freeze the "os" repo and roll everyone over to "os2".
The IBM crowd may feel vindicated at last.
I guess what's old is new again.
I have fuzzy memories on reading about it.
The problem was I think something to do with like the number of git objects that it was scaling to causing crazy server load or something. I don't remember the technical details, but definitely something involving the scale of git objects.
Changes branches took an eternity, and people resorted to a more workspaces style solution.
If you’re planning on starting a big tech company, I wouldn’t recommend the approach.
google1 = code written by Larry, Sergey and employee number 1 (Craig). A hacky pile of Python scripts, dumped fairly quickly.
google2 = the first properly engineered C++ codebase. Protobufs etc were in google2. But the build system was some jungle of custom Makefiles, or something like that. I never saw it directly.
google3 = the same code as google2 but with a new custom build system that used Python scripts to generate Makefiles. I suppose it required a new repository so they could port everything over in parallel with code being worked on in google2. P4 was apparently not that great at branches and google3 didn't use them. Later the same syntax for the build files was kept but turned into a new languages called Starlark and the Makefile generator went away in favor of Blaze, which directly interpreted them.
At least, that's the story I vaguely recall.
But not the 3rd mono repo on the same technology to avoid some scaling limit.
I think what happened is Google bought a license for source code and customised it.
That makes sense because vanilla Perforce is unbearably slow and impossible to scale.
Last I checked, it was bought by Private Equity firms and actual product development had more or less stopped.
The efforts to sell priest robes to fruit vendors were a little silly, but I'm glad they didn't catch on because if they had caught on they no longer would have been silly.
0: https://en.wikipedia.org/wiki/The_Cathedral_and_the_Bazaar