lib: remove unnecessary assignments with _extend

The first parameter to `util._extend` is the target object. Assigning
the target object to the result of `util._extend` is not necessary.

PR-URL: #11364

Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

lib/_http_agent.js

@@ -121,7 +121,7 @@ Agent.prototype.addRequest = function addRequest(req, options) {
   }
 
   options = util._extend({}, options);
-  options = util._extend(options, this.options);
+  util._extend(options, this.options);
 
   if (!options.servername) {
     options.servername = options.host;
@@ -176,7 +176,7 @@ Agent.prototype.addRequest = function addRequest(req, options) {
 Agent.prototype.createSocket = function createSocket(req, options, cb) {
   var self = this;
   options = util._extend({}, options);
-  options = util._extend(options, self.options);
+  util._extend(options, self.options);
 
   if (!options.servername) {
     options.servername = options.host;

lib/_tls_wrap.js

@@ -978,9 +978,9 @@ function normalizeConnectArgs(listArgs) {
   // the host/port/path args that it knows about, not the tls options.
   // This means that options.host overrides a host arg.
   if (listArgs[1] !== null && typeof listArgs[1] === 'object') {
-    options = util._extend(options, listArgs[1]);
+    util._extend(options, listArgs[1]);
   } else if (listArgs[2] !== null && typeof listArgs[2] === 'object') {
-    options = util._extend(options, listArgs[2]);
+    util._extend(options, listArgs[2]);
   }
 
   return (cb) ? [options, cb] : [options];

lib/child_process.js

@@ -133,7 +133,7 @@ exports.execFile = function(file /*, args, options, callback*/) {
   }
 
   if (pos < arguments.length && typeof arguments[pos] === 'object') {
-    options = util._extend(options, arguments[pos++]);
+    util._extend(options, arguments[pos++]);
   } else if (pos < arguments.length && arguments[pos] == null) {
     pos++;
   }

lib/internal/cluster/master.js

@@ -48,8 +48,8 @@ cluster.setupMaster = function(options) {
     execArgv: process.execArgv,
     silent: false
   };
-  settings = util._extend(settings, cluster.settings);
-  settings = util._extend(settings, options || {});
+  util._extend(settings, cluster.settings);
+  util._extend(settings, options || {});
 
   // Tell V8 to write profile data for each process to a separate file.
   // Without --logfile=v8-%p.log, everything ends up in a single, unusable
@@ -110,7 +110,7 @@ function createWorkerProcess(id, env) {
   var execArgv = cluster.settings.execArgv.slice();
   var debugPort = 0;
 
-  workerEnv = util._extend(workerEnv, env);
+  util._extend(workerEnv, env);
   workerEnv.NODE_UNIQUE_ID = '' + id;
 
   for (var i = 0; i < execArgv.length; i++) {