nix config for easier start

[przemek-pokrywka]

Hey :) For anybody who'd like to start toying with the examples without going through the process of setting things up, I've prepared the following nix config (to be put into shell.nix file at the top of the repository):

{ java ? "openjdk8" }:

let
  jdk = pkgs.${java};

  config = {
    packageOverrides = p: rec {
      sbt = p.sbt.overrideAttrs (
        old: rec {
          patchPhase = ''
            echo -java-home ${jdk} >> conf/sbtopts
          '';
        }
      );
    };
  };

  nixpkgs = builtins.fetchTarball {
    name   = "nixos-21.05";
    url    = "https://github.com/NixOS/nixpkgs/archive/refs/tags/21.05.tar.gz";
    sha256 = "1ckzhh24mgz6jd1xhfgx0i9mijk6xjqxwsshnvq789xsavrmsc36";
  };

  pkgs = import nixpkgs { inherit config; };
in
  pkgs.mkShell {
    buildInputs = [
      pkgs.yarn
      pkgs.terraform
      jdk
      pkgs.sbt
    ];
  }