nix-community/nh — reverse-engineered prompt

Build me a polished Rust command line tool called nh that makes everyday Nix work easier and nicer to use. I want one friendly command that brings together common workflows for NixOS, Home Manager, Nix Darwin, package search, cleanup, and generation management.

It should help users switch or test their system or home config, show a clear build tree while things are building, and show an easy to read diff of what will change before activation. Add a fast search command for Nixpkgs, plus a safer cleanup command that can remove old generations, clean leftover roots, and keep recent items based on count or age.

Make the terminal output attractive but still practical. The commands should have helpful help text, sensible defaults, and work with flakes as well as older style configs where possible. Include support for selecting or ignoring specialisations, inspecting generations, and rolling back when needed.

Look up current Nix docs online if you need to.