Add Nix flake

[benjajaja]

Since it's a flake, it should rely on Cargo.lock and not require maintenance, except when a new system dependency is added, which is rare with cargo. Currently the only ones are openssl and pkg-config.

[ulyssa]

Thanks for adding this!

Is there a reason to use pkgs.rust-bin.nightly."2023-03-17".default over pkgs.rust-bin.stable.latest.default like you had it initially? I don't know much about Nix, but I would assume that stable would update automatically over time, right?

[benjajaja]

The reason was that .rs files are formatted with rust-fmt of nightly. Or at least that's what's happening with my nvim+lsp+rust installation. Also perhaps iamb used to require nightly to build some time ago? I don't remember exactly.

Anyway, yay iamb builds against stable, changed that, but only left nightly for the devShell feature. The devShell is pinned to some random recent nightly build so that it caches and doesn't recreate a new derivation every day when a new nightly comes out.

[ulyssa]

Ah, that makes sense. Yeah, you'd need a nightly build for rust-fmt.

I've merged this into main. Thanks for adding this! :) I'll update the website to mention it when I do the next release.

[meain]

FYI, I'm maintaining it in nixpkgs as well.