Microsoft forked git and layered their own file system on top of it to support a centralized git workflow so that they could have a monorepo.
No one should work on monorepos because...
monorepos are bad because...
git can't easily handle them and we shouldn't fix that because...
No one should work on monorepos...
If you think that git needs to be "fixed" or "updated" to support a centralized vcs server to do partial updates over the network, then I think you've missed the point of git.
If you want a centralized, trunk-based version control, don't use git.
It's funny how each company decides to solve these problems.
Google called in the computer scientists and designed a better centralized vcs for their purposes. Good on them. It'd be great if they open sourced it. So typical of Google to invent their own thing and keep it private.
Microsoft took the most popular vcs (git), and inserted a shim layer to make it compatible with their use case. How expected that Microsoft would build a compatibility shim that attempts to hide complexity from the end user.
Meanwhile, Linux and Git are plugging along just fine, in their own separate repos, even though many people work on both projects.
Yeah like their build system... Bazel, that's completely closed source.
It would be hard to open source if its dependencies only exist on Borg. I think that was a problem with Blaze (now Bazel).