docs/nixpkgs-doc/nixpkgs-doc.nix

{ stdenv, inputs }:
stdenv.mkDerivation {
  pname = "nixpkgs-doc-src";
  version = "unstable";

  src = inputs.nixpkgs.outPath;

  phases = "installPhase";

  installPhase = ''
    cp -r doc/ $out
  '';
}