Add zx compression - issue #93

You can now choose 'xz' for your target compression.
For this to work you must have the 'xz' binary installed
and available in your path.

To install the xz compressor you can do something like:
  Debian: apt-get install xz-utils
  OSX:    brew install xz

src/Backup/Target/Compression/Factory.php

@@ -24,6 +24,7 @@ class Factory
     protected static $availableCompressors = [
         'gzip'  => 'Gzip',
         'bzip2' => 'Bzip2',
+        'xz'    => 'Xz',
         'zip'   => 'Zip'
     ];
 

src/Backup/Target/Compression/Xz.php

@@ -0,0 +1,44 @@
+<?php
+namespace phpbu\App\Backup\Target\Compression;
+
+/**
+ * Xz
+ *
+ * @package    phpbu
+ * @subpackage Backup
+ * @author     Sebastian Feldmann <sebastian@phpbu.de>
+ * @copyright  Sebastian Feldmann <sebastian@phpbu.de>
+ * @license    https://opensource.org/licenses/MIT The MIT License (MIT)
+ * @link       http://phpbu.de/
+ * @since      Class available since Release 5.0.0
+ */
+class Xz extends Abstraction
+{
+    /**
+     * Command name
+     *
+     * @var string
+     */
+    protected $cmd = 'xz';
+
+    /**
+     * Suffix for compressed files
+     *
+     * @var string
+     */
+    protected $suffix = 'xz';
+
+    /**
+     * MIME type for compressed files
+     *
+     * @var string
+     */
+    protected $mimeType = 'application/x-xz';
+
+    /**
+     * Can this compression compress piped output
+     *
+     * @var bool
+     */
+    protected $pipeable = true;
+}

src/Cli/Executable/Tar.php

@@ -79,6 +79,7 @@ class Tar extends Abstraction implements Executable
     private static $availableCompressions = [
         'bzip2' => 'j',
         'gzip'  => 'z',
+        'xz'    => 'J'
     ];
 
     /**

tests/phpbu/Backup/Target/CompressionTest.php

@@ -47,6 +47,17 @@ public function testBzip2()
         $this->assertEquals('application/x-bzip2', $gzip->getMimeType());
     }
 
+    /**
+     * Test xz compressor
+     */
+    public function testXz()
+    {
+        $gzip = Compression\Factory::create('xz');
+        $this->assertEquals('xz', $gzip->getSuffix());
+        $this->assertEquals('xz', $gzip->getCommand());
+        $this->assertEquals('application/x-xz', $gzip->getMimeType());
+    }
+
     /**
      * Test Compression::isPipeable
      */
@@ -58,6 +69,9 @@ public function testIsPipeable()
         $bzip = Compression\Factory::create('bzip2');
         $this->assertTrue($bzip->isPipeable());
 
+        $xz = Compression\Factory::create('xz');
+        $this->assertTrue($bzip->isPipeable());
+
         $zip = Compression\Factory::create('zip');
         $this->assertFalse($zip->isPipeable());
     }