Move default.nix to shell.nix

upstream.nix

@@ -1,14 +1,21 @@
 { nixpkgs ? import <nixpkgs> {} }:
 
 let
-  inherit (nixpkgs) stdenv git tup pkg-config;
-  toolchain = import ./tool/toolchain.nix { inherit nixpkgs; };
+  inherit (nixpkgs) stdenv fetchgit git tup pkg-config;
+
+  toolchain = import ./toolchain.nix { inherit nixpkgs; };
+  version = "19.07-322-gfe24051cd";
 in
 stdenv.mkDerivation {
   name = "genode";
   outputs = [ "out" "dev" ];
+  inherit version;
 
-  src = ./../genode;
+  src = fetchgit {
+    url = "git://depot.h4ck.me/srv/git/genode";
+    rev = "fe24051cd811d5e769104ffd7228d35a72a3d93c";
+    sha256 = "09wl7q1xc7fvnj8zcb4ix1ipqzxrgp6sbdsqp92r2gxqkadyrpxc";
+  };
 
   nativeBuildInputs =
     [ toolchain
@@ -27,7 +34,7 @@ stdenv.mkDerivation {
       # Use specialized build configuration
       substitute configs/nix-x86_64.config tup.config \
         --replace @NIX_DEV_OUTPUT@ $dev \
-        --replace @NIX_DEPOT_VERSION@ `git describe` \
+        --replace @NIX_DEPOT_VERSION@ ${version} \
 
       # Scan repository and generate script
       mkdir lib