Direnv nix config files for installing specific version on the fly cli when entering project dir.

.envrc

use nix

shell.nix

with import <nixpkgs> {};
let
  pinFly = self: super: {
    fly = super.fly.overrideAttrs (old: {
      version = "6.0.0";

      src = fetchFromGitHub {
        owner = "concourse";
        repo = "concourse";
        rev = "v6.0.0";
        sha256 = "0chavwymyh5kv4fkvdjvf3p5jjx4yn9aavq66333xnsl5pn7q9dq";
      };

      vendorSha256 = null;
      deleteVendor = true;
      preBuild = ''
        unset GOPROXY
        go mod vendor
      '';

      buildFlagsArray = ''
          -ldflags=
          -X github.com/concourse/concourse.Version=6.0.0
        '';
    });
  };

  pinPkgs = import <nixpkgs> { overlays = [ pinFly ]; };
in
pkgs.mkShell {
  nativeBuildInputs = [ pinPkgs.fly ];
}