nginx: Format the config file

nixos/modules/services/web-servers/nginx/default.nix

@@ -16,7 +16,20 @@ let
   ) cfg.virtualHosts;
   enableIPv6 = config.networking.enableIPv6;
 
-  configFile = pkgs.writeText "nginx.conf" ''
+  configFile = pkgs.runCommand "nginx.conf" {
+    inherit configFileUnformatted;
+    passAsFile = [ "configFileUnformatted" ];
+    # configFileUnformatted is created locally, therefore so should this be.
+    preferLocalBuild = true;
+    allowSubstitutes = false;
+  } ''
+    cp ${configFileUnformatted} nginx.conf
+    chmod u+w nginx.conf
+    ${pkgs.nginx-config-formatter}/bin/nginxfmt nginx.conf
+    cp nginx.conf $out
+  '';
+
+  configFileUnformatted = pkgs.writeText "nginx.unformatted.conf" ''
     user ${cfg.user} ${cfg.group};
     error_log stderr;
     daemon off;