add nodeinfo package

pkgs/nodeinfo.nix

@@ -0,0 +1,14 @@
+with import <nixpkgs> {}; # bring all of Nixpkgs into scope
+
+stdenv.mkDerivation {
+  name = "nodeinfo";
+  src = ./nodeinfo.sh;
+
+  unpackPhase = "true";
+  installPhase = ''
+    mkdir -p $out
+    mkdir -p $out/bin
+    chmod +wx $src
+    cp $src $out/bin/nodeinfo
+    '';
+}

pkgs/nodeinfo.sh

@@ -0,0 +1,8 @@
+sleep 5
+OUTFILE=/var/lib/nodeinfo.nix
+rm -f $OUTFILE
+{
+    echo \{
+    echo "  bitcoind_onion = \"$(cat /var/lib/tor/onion/bitcoind/hostname)\";"
+    echo \}
+} > $OUTFILE