add generate-secrets pkg

generate-secrets.sh will also be used in generate-secrets.nix, so DRY
its dependency definitions.

pkgs/default.nix

@@ -9,4 +9,5 @@
   hwi = pkgs.callPackage ./hwi { };
   pylightning = pkgs.python3Packages.callPackage ./pylightning { };
   liquid-swap = pkgs.python3Packages.callPackage ./liquid-swap { };
+  generate-secrets = pkgs.callPackage ./generate-secrets { };
 }

pkgs/generate-secrets/default.nix

@@ -0,0 +1,6 @@
+{ pkgs }: with pkgs;
+
+writeScript "generate-secrets" ''
+  export PATH=${lib.makeBinPath [ coreutils apg openssl ]}
+  . ${./generate-secrets.sh} ${./openssl.cnf}
+''

shell.nix

@@ -7,8 +7,9 @@ stdenv.mkDerivation rec {
   name = "nix-bitcoin-environment";
 
   nixops19_09 = callPackage ./pkgs/nixops {};
+  generate-secrets = callPackage ./pkgs/generate-secrets {};
 
-  buildInputs = with pkgs; [ nixops19_09 figlet apg openssl ];
+  buildInputs = [ nixops19_09 figlet ];
 
   shellHook = ''
     export NIX_PATH="nixpkgs=${nixpkgs}:."
@@ -18,6 +19,6 @@ stdenv.mkDerivation rec {
     # keys already added to my ssh-agent.
     export SSH_AUTH_SOCK=""
     figlet "nix-bitcoin"
-    (cd secrets; ./generate_secrets.sh)
+    (mkdir -p secrets; cd secrets; ${generate-secrets})
   '';
 }