feat(third_party): Add nixery with Cachix configuration

default.nix

@@ -4,6 +4,8 @@
 # This makes packages accessible via the Nixery instance that is configured to
 # use this repository as its nixpkgs source.
 
+with builtins;
+
 let
   localPkgs = super: pkgs: {
     # Local projects should be added here:
@@ -14,6 +16,7 @@ let
 
     # Third-party projects (either vendored or modified from nixpkgs) go here:
     gitAppraise = pkgs.callPackage ./third_party/go/git-appraise/git-appraise {};
+    nixery = import ./third_party/nixery.nix { pkgs = super; };
     terraform-gcp = pkgs.terraform_0_12.withPlugins(p: [ p.google ]);
   };
 
@@ -22,7 +25,7 @@ let
   nixpkgsVersion = "88d9f776091896cfe57dc6fbdf246e7d27d5f105";
   nixpkgs = "https://github.com/NixOS/nixpkgs-channels/archive/${nixpkgsVersion}.tar.gz";
 
-in { ... } @ args: import (builtins.fetchTarball nixpkgs) (args // {
+in { ... } @ args: import (fetchTarball nixpkgs) (args // {
     overlays = [ localPkgs ];
     config.allowUnfree = true;
 })

third_party/nixery.nix

@@ -0,0 +1,18 @@
+# Technically I suppose Nixery is not a third-party program, but it's
+# outside of this repository ...
+{ pkgs }:
+
+let src = pkgs.fetchFromGitHub {
+  owner = "google";
+  repo = "nixery";
+  rev = "5d64be1969f397236883f140b4d533497622387c";
+  sha256 = "0vxng5iy6m5a9b38x1mama6idagdinlv001fdkmjgj25sgyrqy2h";
+};
+in import src {
+  inherit pkgs;
+  preLaunch = ''
+    export USER=root
+    cachix use tazjin
+  '';
+  extraPackages = with pkgs; [ cachix iana-etc ];
+}