Reorder ArchiveManager parameters to make the download manager optional

src/Composer/Factory.php

@@ -319,12 +319,12 @@ class Factory
     }
 
     /**
-     * @param Downloader\DownloadManager $dm      Manager use to download sources
      * @param Config                     $config  The configuration
+     * @param Downloader\DownloadManager $dm      Manager use to download sources
      *
      * @return Archiver\ArchiveManager
      */
-    public function createArchiveManager(DownloadManager $dm = null, Config $config)
+    public function createArchiveManager(Config $config, DownloadManager $dm = null)
     {
         if (null === $dm) {
             $dm = $this->createDownloadManager(new IO\NullIO(), $config);

tests/Composer/Test/Package/Archiver/ArchiveManagerTest.php

@@ -32,7 +32,7 @@ class ArchiveManagerTest extends ArchiverTest
         parent::setUp();
 
         $factory = new Factory();
-        $this->manager = $factory->createArchiveManager(null, $factory->createConfig());
+        $this->manager = $factory->createArchiveManager($factory->createConfig());
         $this->targetDir = $this->testDir.'/composer_archiver_tests';
     }