[Console] Added Command::isEnabled method that defines whether to add the command or not

src/Symfony/Component/Console/Application.php

@@ -388,6 +388,11 @@ class Application
     {
         $command->setApplication($this);
 
+        if (!$command->isEnabled()) {
+            $command->setApplication(null);
+            return;
+        }
+
         $this->commands[$command->getName()] = $command;
 
         foreach ($command->getAliases() as $alias) {

src/Symfony/Component/Console/Command/Command.php

@@ -116,6 +116,19 @@ class Command
         return $this->application;
     }
 
+    /**
+     * Checks whether the command is enabled or not in the current environment
+     *
+     * Override this to check for x or y and return false if the command can not
+     * run properly under the current conditions.
+     *
+     * @return Boolean
+     */
+    public function isEnabled()
+    {
+        return true;
+    }
+
     /**
      * Configures the current command.
      */