util: add util._extend for extending objects

There were 2 duplicates with such functionality in `cluster` and
`child_process` modules which were replaced by this function.

lib/child_process.js

@@ -22,7 +22,7 @@
 var EventEmitter = require('events').EventEmitter;
 var net = require('net');
 var Process = process.binding('process_wrap').Process;
-var inherits = require('util').inherits;
+var util = require('util');
 var constants; // if (!constants) constants = process.binding('constants');
 
 var Pipe;
@@ -53,19 +53,6 @@ function createSocket(pipe, readable) {
   return s;
 }
 
-function mergeOptions(target, overrides) {
-  if (overrides) {
-    var keys = Object.keys(overrides);
-    for (var i = 0, len = keys.length; i < len; i++) {
-      var k = keys[i];
-      if (overrides[k] !== undefined) {
-        target[k] = overrides[k];
-      }
-    }
-  }
-  return target;
-}
-
 
 function setupChannel(target, channel) {
   target._channel = channel;
@@ -244,7 +231,7 @@ exports.exec = function(command /*, options, callback */) {
     args = ['/s', '/c', '"' + command + '"'];
     // Make a shallow copy before patching so we don't clobber the user's
     // options object.
-    options = mergeOptions({}, options);
+    options = util._extend({}, options);
     options.windowsVerbatimArguments = true;
   } else {
     file = '/bin/sh';
@@ -281,7 +268,7 @@ exports.execFile = function(file /* args, options, callback */) {
   }
 
   // Merge optionArg into options
-  mergeOptions(options, optionArg);
+  util._extend(options, optionArg);
 
   var child = spawn(file, args, {
     cwd: options.cwd,
@@ -430,7 +417,7 @@ function ChildProcess() {
     maybeExit(self);
   };
 }
-inherits(ChildProcess, EventEmitter);
+util.inherits(ChildProcess, EventEmitter);
 
 
 function setStreamOption(name, index, options) {

lib/cluster.js

@@ -29,18 +29,6 @@ function isObject(o) {
   return (typeof o === 'object' && o !== null);
 }
 
-function extendObject(origin, add) {
-  // Don't do anything if add isn't an object
-  if (!add) return origin;
-
-  var keys = Object.keys(add),
-      i = keys.length;
-  while (i--) {
-    origin[keys[i]] = add[keys[i]];
-  }
-  return origin;
-}
-
 var debug;
 if (process.env.NODE_DEBUG && /cluster/.test(process.env.NODE_DEBUG)) {
   debug = function(x) {
@@ -138,7 +126,7 @@ function isInternalMessage(message) {
 
 // Modyfi message object to be internal
 function internalMessage(inMessage) {
-  var outMessage = extendObject({}, inMessage);
+  var outMessage = util._extend({}, inMessage);
 
   // Add internal prefix to cmd
   outMessage.cmd = INTERNAL_PREFIX + (outMessage.cmd || '');
@@ -172,7 +160,7 @@ var messageHandingObject = {};
 function handleMessage(worker, inMessage, inHandle) {
 
   //Remove internal prefix
-  var message = extendObject({}, inMessage);
+  var message = util._extend({}, inMessage);
   message.cmd = inMessage.cmd.substr(INTERNAL_PREFIX.length);
 
   var respondUsed = false;
@@ -276,11 +264,11 @@ function Worker(customEnv) {
 
     // Create env object
     // first: copy and add uniqueID
-    var envCopy = extendObject({}, env);
+    var envCopy = util._extend({}, env);
     envCopy['NODE_UNIQUE_ID'] = this.uniqueID;
     // second: extend envCopy with the env argument
     if (isObject(customEnv)) {
-      envCopy = extendObject(envCopy, customEnv);
+      envCopy = util._extend(envCopy, customEnv);
     }
 
     // fork worker

lib/util.js

@@ -506,3 +506,15 @@ exports.inherits = function(ctor, superCtor) {
     }
   });
 };
+
+exports._extend = function(origin, add) {
+  // Don't do anything if add isn't an object
+  if (!add) return origin;
+
+  var keys = Object.keys(add);
+  var i = keys.length;
+  while (i--) {
+    origin[keys[i]] = add[keys[i]];
+  }
+  return origin;
+};