use the pinned nixpkgs for the shell

shell.nix

@@ -1,11 +1,5 @@
 let
-  p = import <nixpkgs> {};
-  pkgs = import (p.fetchFromGitHub {
-    owner = "NixOS";
-    repo = "nixpkgs-channels";
-    rev = "cfafd6f5a819472911eaf2650b50a62f0c143e3e";
-    sha256 = "10xgiyh4hbwwiy8qg70ma1f27nd717aflksk9fx3ci8bmxmqbkkn";
-  }) {};
+  pkgs = import ./nix {};
 
 
   inherit (pkgs) stdenv;
@@ -14,6 +8,7 @@ let
     name = "gh-event-forwarder";
     src = null;
     buildInputs = with pkgs; [
+      nix-prefetch-git
       php
       phpPackages.composer
       nix
@@ -23,17 +18,19 @@ let
       bash
     ];
 
-    HISTFILE = "${src}/.bash_hist";
+    # HISTFILE = "${src}/.bash_hist";
     passthru.rustEnv = rustEnv;
   };
 
   rustEnv = stdenv.mkDerivation rec {
     name = "gh-event-forwarder";
     buildInputs = with pkgs; [
-      php
-      phpPackages.composer
+      nix-prefetch-git
+      #php
+      #phpPackages.composer
       rust.rustc
       rust.cargo
+      carnix
       openssl.dev
       pkgconfig
     ];