nix env for reproductible devenv and build

.envrc

@@ -0,0 +1 @@
+use_nix

aggreact.cabal

@@ -1,8 +1,10 @@
--- This file has been generated from package.yaml by hpack version 0.28.2.
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.31.2.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 2c0743c70d80e2ac0827c17be0cfb1ca6bfd0a613a186d520ce3faeddd522550
+-- hash: cd60f98ce5adc1993e4769824e33298d5d80b96bd03e156d69698fae38f4ef5c
 
 name:           aggreact
 version:        0.1.0.0
@@ -16,7 +18,6 @@ copyright:      © 2018 Yann Esposito
 license:        ISC
 license-file:   LICENSE
 build-type:     Simple
-cabal-version:  >= 1.10
 extra-source-files:
     README.md
     stack.yaml

nix/nixpkgs.json

@@ -0,0 +1,7 @@
+{
+  "url": "https://github.com/nixos/nixpkgs.git",
+  "rev": "e03966a60f517700f5fee5182a5a798f8d0709df",
+  "date": "2019-04-03T21:17:44+02:00",
+  "sha256": "1jwgzfnjgfcr67c7nz8hkw4a13qa296bv5cr6m36pfydw27aqdas",
+  "fetchSubmodules": false
+}

nix/nixpkgs.nix

@@ -0,0 +1,10 @@
+{ }:
+let
+  hostpkgs = import <nixpkgs> {};
+  srcDef = builtins.fromJSON (builtins.readFile ./nixpkgs.json);
+  nixpkgs = hostpkgs.fetchFromGitHub {
+    owner = "NixOS";
+    repo = "nixpkgs";
+    inherit (srcDef) rev sha256;
+  };
+in import nixpkgs { }

nix/update-nixpkgs-dev.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p nix-prefetch-git
+
+nix-prefetch-git https://github.com/nixos/nixpkgs.git > ./nix/nixpkgs.json

nix/update-nixpkgs.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p nix-prefetch-git
+
+nix-prefetch-git https://github.com/nixos/nixpkgs-channels.git \
+                 --rev refs/heads/nixos-unstable > ./nix/nixpkgs.json

shell.nix

@@ -0,0 +1,12 @@
+with import nix/nixpkgs.nix {};
+
+mkShell {
+  name = "aggreact";
+  buildInputs = [ gnupg
+                  haskellPackages.stack
+                  haskellPackages.ghcid
+                ];
+  LC_ALL = "en_US.UTF-8";
+  LANG = "en_US.UTF-8";
+  TMPDIR = "/tmp";
+}