minor #5425 Added a caution note about invoking other commands (kix, javiereguiluz)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5425).

Discussion
----------

Added a caution note about invoking other commands

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets | -

This PR finishes #4493. That's why is committed against `master` branch, but it should be merged in 2.3+.

Commits
-------

2c491be Fixed typos
b86ffb6 Removed duplication and moved a caution message
57938a5 [Console] Added a cookbook entry on invoking other commands

Author: weaverryan

components/console/introduction.rst

@@ -449,6 +449,8 @@ method::
     You can also test a whole console application by using
     :class:`Symfony\\Component\\Console\\Tester\\ApplicationTester`.
 
+.. _calling-existing-command:
+
 Calling an Existing Command
 ---------------------------
 
@@ -478,16 +480,27 @@ Calling a command from another one is straightforward::
     }
 
 First, you :method:`Symfony\\Component\\Console\\Application::find` the
-command you want to execute by passing the command name.
-
-Then, you need to create a new
-:class:`Symfony\\Component\\Console\\Input\\ArrayInput` with the arguments and
-options you want to pass to the command.
+command you want to execute by passing the command name. Then, you need to create
+a new :class:`Symfony\\Component\\Console\\Input\\ArrayInput` with the arguments
+and options you want to pass to the command.
 
 Eventually, calling the ``run()`` method actually executes the command and
 returns the returned code from the command (return value from command's
 ``execute()`` method).
 
+.. 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 the commands will run in the same process and some of Symfony's
+    built-in commands may not work well this way. For instance, the ``cache:clear``
+    and ``cache:warmup`` commands change some class definitions, so running
+    something after them is likely to break.
+
 .. note::
 
     Most of the time, calling a command from code that is not executed on the

cookbook/console/console_command.rst

@@ -150,6 +150,12 @@ 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
+-----------------------
+
+See :ref:`calling-existing-command` if you need to implement a command that runs
+other dependent commands.
+
 Testing Commands
 ----------------