feature #21578 [Translation] Added a lint:xliff command for XLIFF files (javiereguiluz)

This PR was squashed before being merged into the 3.3-dev branch (closes #21578).

Discussion
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[Translation] Added a lint:xliff command for XLIFF files

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #19942
| License       | MIT
| Doc PR        | -

It works exactly the same as the `lint:yaml` command:

### Lint a single file
![single-file](https://cloud.githubusercontent.com/assets/73419/22821214/6b459454-ef7a-11e6-9320-029c22ab8803.png)

### Lint a bundle

![bundle](https://cloud.githubusercontent.com/assets/73419/22821215/6c2c0196-ef7a-11e6-9de0-a1816eede9b3.png)

### Get the result in JSON

![json](https://cloud.githubusercontent.com/assets/73419/22829844/bacaa68e-efa4-11e6-9341-0c3d4821c5c7.png)

Commits
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7609e440ff [Translation] Added a lint:xliff command for XLIFF files

Author: fabpot

Command/XliffLintCommand.php

@@ -0,0 +1,80 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Bundle\FrameworkBundle\Command;
+
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Translation\Command\XliffLintCommand as BaseLintCommand;
+
+/**
+ * Validates XLIFF files syntax and outputs encountered errors.
+ *
+ * @author Grégoire Pineau <lyrixx@lyrixx.info>
+ * @author Robin Chalas <robin.chalas@gmail.com>
+ * @author Javier Eguiluz <javier.eguiluz@gmail.com>
+ */
+class XliffLintCommand extends Command
+{
+    private $command;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function configure()
+    {
+        $this->setName('lint:xliff');
+
+        if (!$this->isEnabled()) {
+            return;
+        }
+
+        $directoryIteratorProvider = function ($directory, $default) {
+            if (!is_dir($directory)) {
+                $directory = $this->getApplication()->getKernel()->locateResource($directory);
+            }
+
+            return $default($directory);
+        };
+
+        $isReadableProvider = function ($fileOrDirectory, $default) {
+            return 0 === strpos($fileOrDirectory, '@') || $default($fileOrDirectory);
+        };
+
+        $this->command = new BaseLintCommand(null, $directoryIteratorProvider, $isReadableProvider);
+
+        $this
+            ->setDescription($this->command->getDescription())
+            ->setDefinition($this->command->getDefinition())
+            ->setHelp($this->command->getHelp().<<<'EOF'
+
+Or find all files in a bundle:
+
+  <info>php %command.full_name% @AcmeDemoBundle</info>
+
+EOF
+            );
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isEnabled()
+    {
+        return class_exists(BaseLintCommand::class);
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        return $this->command->execute($input, $output);
+    }
+}