Add Nix VM configuration for local testing

.gitignore

@@ -1,2 +1,3 @@
 /web-serve
 *.pyc
+/nixos.qcow2

vm.nix

@@ -0,0 +1,34 @@
+# Nix configuration.  Install and run with e.g. nixos-shell
+# (https://github.com/Mic92/nixos-shell) to create and run this webserver.
+{ config, lib, pkgs, ... }:
+
+{
+  virtualisation.qemu.networkingOptions = [
+    # We need to re-define our usermode network driver
+    # since we are overriding the default value.
+    "-net nic,netdev=user.0,model=virtio"
+    # Than we can use qemu's hostfwd option to forward ports.
+    "-netdev user,id=user.0,hostfwd=tcp::8080-:80"
+  ];
+
+  nixos-shell.mounts = {
+    mountHome = false;
+    mountNixProfile = false;
+    extraMounts = {
+      "/var/www" = ./.;
+    };
+  };
+
+  services.nginx = {
+    enable = true;
+    recommendedGzipSettings = true;
+    recommendedOptimisation = true;
+    virtualHosts."localhost" = {
+      root = "/var/www/web-serve";
+      locations."/".extraConfig = ''
+      error_page 404 /404.html;
+      try_files $uri $uri.html $uri/ =404;
+      '';
+    };
+  };
+}