* nix-flake: use follows for `rust-overlay` (..)
This removes the extra nixpkgs dependency by re-using the nixpkgs
already defined.
https://nixos.wiki/wiki/Flakeshttps://web.archive.org/web/20230621091703/https://nixos.wiki/wiki/Flakes
> # The `follows` keyword in inputs is used for inheritance.
> # Here, `inputs.nixpkgs` of sops-nix is kept consistent with the `inputs.nixpkgs` of
> # the current flake, to avoid problems caused by different versions of nixpkgs.
* nix-flake: use nix overlays for rustc/cargo (..)
This allows the same nightly rust version to be used across the
flake (vs. strictly in the `devShell`).
* nix-flake: add `mdbook` to the development shell (..)
bumped `nixpkgs` to the latest unstable to pull in mdbook version `0.4.30`.
* nix-flake: expose all rust tools in dev environment (..)
The `oxalica / rust-overlay` docs expose all tools in the development
environment, so we should do the same:
https://github.com/oxalica/rust-overlay#use-in-devshell-for-nix-develop
---------
Co-authored-by: Jay Querie <jay@querie.cc>
