The right way to do 'bundle config --local'

As showed at ‘Bundler: bundle config’,
The local configuration will be stored in app/.bundle/config .

What’s the right way to do ‘bundle config --local’ in nix-shell?

bundle config does not read app/.bundle/config in nix-shell.

shell.nix

with (import <nixpkgs> {});
let
  env = bundlerEnv {
    name = "rails_tutorial-bundler-env";
    inherit ruby;
    gemfile  = ./Gemfile;
    lockfile = ./Gemfile.lock;
    gemset   = ./gemset.nix;
    groups = [ "default" "development" "test" ];
  };
in stdenv.mkDerivation {
  name = "rails_tutorial";
  buildInputs = [ env ruby nodejs ];
}

rails_tutorial/.bundle/config

---
BUNDLE_WITHOUT: "production"

Can not find without ... in output of bundle config?

$ nix-shell
$ bundle config
Settings are listed in order of priority. The top value will be used.

gemfile
Set via BUNDLE_GEMFILE: "/nix/store/5am98ssn5kjlqlyvz7mx9pvgjsvk23sk-gemfile-and-lockfile/Gemfile"

path
Set via BUNDLE_PATH: "/nix/store/x8vc28lr0r2ksvly9hh46fzrkcxzy99y-rails_tutorial-bundler-env/lib/ruby/gems/2.5.0"

frozen
Set via BUNDLE_FROZEN: true

bin_path
Set via BUNDLE_BIN_PATH: "/nix/store/x8vc28lr0r2ksvly9hh46fzrkcxzy99y-rails_tutorial-bundler-env/lib/ruby/gems/2.5.0/gems/bundler-1.17.2/exe/bundle"