Add env for nix-shell which pins nixpkgs and automatically creates secrets

env.nix

@@ -0,0 +1,20 @@
+let
+  # Pin nixpkgs
+  nixpkgs = builtins.fetchGit {
+    url = "https://github.com/nixos/nixpkgs-channels";
+    ref = "nixos-18.09";
+    rev = "0396345b79436f54920f7eb651ab42acf2eb7973";
+  };
+in
+with import nixpkgs { };
+
+stdenv.mkDerivation rec {
+  name = "nix-bitcoin-environment";
+
+  buildInputs = [ pkgs.nixops pkgs.figlet pkgs.apg ];
+
+  shellHook = ''
+    figlet "nix-bitcoin"
+    ./secrets/generate_secrets.sh
+  '';
+}

secrets/generate_secrets.sh

@@ -1,15 +1,13 @@
 #!/bin/bash
 
 SECRETSFILE=secrets/secrets.nix
-mkdir -p secrets
 
 if [ -e "$SECRETSFILE" ]; then
-    echo $SECRETSFILE already exists
+    echo $SECRETSFILE already exists. No new secrets were generated.
     exit 1
 fi
 
 echo Installing apg through nix-env
-nix-env -i apg
 echo Write secrets to $SECRETSFILE
 {
     echo \{