Multiple improvements and refactorizations

lib/initca.nix

@@ -1,4 +1,4 @@
-{ pkgs ? import <nixpkgs> {}, ...}:
+{ pkgs ? import <nixpkgs> {}, initca ? "", ...}:
 with pkgs;
 let
   initca' =
@@ -22,11 +22,12 @@ let
         buildInputs = [ pkgs.cfssl ];
       } '' cfssl genkey -initca ${ca_csr} | cfssljson -bare ca; \
            mkdir -p $out; cp *.pem $out'';
+  ca = if initca != "" then initca else initca';
 in
   # make ca derivation sha depend on initca cfssl output
   pkgs.stdenv.mkDerivation {
     name = "ca";
-    src = initca';
+    src = ca;
     buildCommand = ''
       mkdir -p $out;
       cp -r $src/* $out