I'm not sure I'll ever understand why they replaced their working ~50 line shell script with a Rust program that just shells out to the same nix-* commands. I appreciate that there are some safety benefits, but that program is just not complex enough to benefit.

Because it's "a proper language" [1]. Not to mention webscale!

It does seem to do some more complex stuff now that would've been annoying, but not impossible, to write as a shell script.

[1]: https://github.com/nix-community/comma/pull/19

Shell is already memory safe, so there's not even "we replaced C" to lean on.