alt Hacker News> Writing your tooling in python is valid while starting out and prototyping.
This fallacy again. Tell me, when did Mercurial decide "ok the prototype is done, we'll rewrite it in a proper language"?
They didn't, of course. Because nobody ever does. Your "prototype" gradually becomes a 100k line product that you can't afford to rewrite.
(I guess you can YOLO it with AI these days but that wasn't an option for Mercurial.)
> Starting with C was great for performance of Git, but damn if it's not a terrible UX these days
Git's terrible UX doesn't have anything to do with C. C doesn't make you always pick a different flag for "delete".
The Mercurial project has been incrementally rewriting core operations in Rust for several years now. As Pierre-Yves says in the talk, you can do an hg status on a million-file repo in 100ms. I rewrote hg annotate (aka blame) in Rust last year.