Don't output two welcome messages.

Make the dispatched shell task as 'requested'. This disables the welcome
message being output by the task. The containing shell will take care of
emiting the welcome message.

Refs #8600

src/Console/Shell.php

@@ -447,7 +447,7 @@ class Shell
         if ($this->hasTask($command) && isset($subcommands[$command])) {
             $this->startup();
             array_shift($argv);
-            return $this->{$method}->runCommand($argv, false);
+            return $this->{$method}->runCommand($argv, false, ['requested' => true]);
         }
 
         if ($this->hasMethod('main')) {

tests/TestCase/Console/ShellTest.php

@@ -1066,7 +1066,7 @@ TEXT;
         $task->io($io);
         $task->expects($this->once())
             ->method('runCommand')
-            ->with(['one'], false);
+            ->with(['one'], false, ['requested' => true]);
 
         $shell->expects($this->once())->method('getOptionParser')
             ->will($this->returnValue($parser));
@@ -1081,6 +1081,41 @@ TEXT;
     }
 
     /**
+     * test that runCommand will invoke a task
+     *
+     * @return void
+     */
+    public function testRunCommandInvokeTask()
+    {
+        $parser = new ConsoleOptionParser('knife');
+        $parser->addSubcommand('slice');
+        $io = $this->getMock('Cake\Console\ConsoleIo');
+
+        $shell = $this->getMock('Cake\Console\Shell', ['hasTask', 'getOptionParser'], [$io]);
+        $task = $this->getMock('Cake\Console\Shell', ['main', '_welcome'], [$io]);
+
+        $shell->expects($this->once())
+            ->method('getOptionParser')
+            ->will($this->returnValue($parser));
+
+        $shell->expects($this->any())
+            ->method('hasTask')
+            ->will($this->returnValue(true));
+
+        $task->expects($this->never())
+            ->method('_welcome');
+
+        // One welcome message output.
+        $io->expects($this->at(2))
+            ->method('out')
+            ->with($this->stringContains('Welcome to CakePHP'));
+
+        $shell->Slice = $task;
+        $shell->runCommand(['slice', 'one']);
+        $this->assertTrue($task->params['requested'], 'Task is requested, no welcome.');
+    }
+
+    /**
      * test wrapBlock wrapping text.
      *
      * @return void