Feature Request: Show changes in NixOS option definitions

It could be very helpful to see changes in option definitions, whenever a new NixOS module is added or changed in a pull request.

For example, a recent pull request has accidentally enabled Docker by default.

Given that modules could change any other option definition, I think it's a good idea to have a diff of the changed option definitions during review of the pull request.

As an (very raw and unpolished) example, something like this can be used with nix-instantiate --strict --json --eval thefollowingfile.nix from the nixpkgs root to spit out JSON that can be diffed against the output when run against the previous version of nixpkgs:

let
  lib = import ./lib;

  inherit (import ./nixos/lib/eval-config.nix {
    modules = [];
  }) options;

  sanitise = type: val: let
    typename = type.name or null;
    subtype = type.functor.wrapped or null;
  in if typename == "path" then null
     else if lib.isList val then map (sanitise subtype) val
     else if lib.isFunction val then "<function>"
     else if lib.isDerivation val then "<derivation ${val.name}>"
     else if lib.isAttrs val then lib.attrNames val
     else if lib.isBool val || lib.isInt val || isNull val then val
     else toString val;

  recurseCond = opt: !lib.isOption opt;
  sanitiseOpt = path: opt: let
    eval = builtins.tryEval (sanitise opt.type opt.definitions);
  in if opt ? definitions then eval.value else null;

in lib.mapAttrsRecursiveCond recurseCond sanitiseOpt options

The issue provides no ofborg file or test entry point. Start by running the provided nix-instantiate expression from the nixpkgs root and reading nixos/lib/eval-config.nix; define the desired option-definition diff output and pull-request review integration, with a clear example of the Docker default change as the completion criterion.