[Console] Added a cookbook entry on invoking other commands

cookbook/console/console_command.rst

@@ -146,6 +146,40 @@ before translating contents::
 However for other services the solution might be more complex. For more details,
 see :doc:`/cookbook/service_container/scopes`.
 
+Invoking Other Commands
+-----------------------
+
+If you need to implement a command that runs other dependent commands, you can fetch 
+these commands using the :class:`Symfony\\Component\\Console\\Application <Symfony\\Component\\Console\\Application>`'s ``find`` method. 
+
+Also note that you'll have to pass :class:`Symfony\\Component\\Console\\Input\\InputInterface` and :class:`Symfony\\Component\\Console\\Output\\OutputInterface` 
+as arguments to the command's ``execute`` method. This can be easily implemented 
+with :class:`Symfony\\Component\\Console\\Input\\ArrayInput`::
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $command = $this->getApplication()->find('some:command');
+        $command->execute(
+            new ArrayInput(array(
+                'foo' => 'foo', 
+                '--bar' => 'foobar',
+            )), 
+            $output
+        );
+    }
+
+.. tip::
+
+    If you want to suppress the output of the executed command, pass a :class:`Symfony\\Component\\Console\\Output\\NullOutput`
+    as the second argument to ``$command->execute()``.
+
+.. caution::
+
+    Note that all these commands will run in the same process, and some of Symfony's 
+    built-in commands may not work well this way. For instance, ``cache:clear`` and ``cache:warmup`` 
+    commands change some class definitions, so running something 
+    after them is likely to break.
+
 Testing Commands
 ----------------