bug #167 Allow to execute the symfony demo command repeatedly (javiereguiluz)

This PR was merged into the 1.0-dev branch.

Discussion
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Allow to execute the `symfony demo` command repeatedly

If `-> addArgument()` provides a default value for the `directory` argument, then the `!$input->getArgument('directory')` instruction will never be `true`. The result is that you cannot execute the `symfony demo` command repeatedly as you could in the previous versions:

![symfony_demo](https://cloud.githubusercontent.com/assets/73419/8076829/b62051c8-0f50-11e5-9d58-eb9ca33735d0.png)

Commits
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182babb Allow to execute the `symfony demo` command repeatedly

Author: javiereguiluz

src/Symfony/Installer/DemoCommand.php

@@ -30,7 +30,7 @@ protected function configure()
     {
         $this
             ->setName('demo')
-            ->addArgument('directory', InputArgument::OPTIONAL, 'Directory where the new project will be created.', 'symfony_demo')
+            ->addArgument('directory', InputArgument::OPTIONAL, 'Directory where the new project will be created.')
             ->setDescription('Creates a demo Symfony project.')
         ;
     }