Made changes which fied warnings and errors in tests.

src/Composer/Downloader/GitDownloader.php

@@ -48,7 +48,6 @@ class GitDownloader extends VcsDownloader
      */
     protected function enforceCleanDirectory($path)
     {
-        $output = array();
         $this->process->execute(sprintf('cd %s && git status --porcelain', escapeshellarg($path)), $output);
         if (trim($output)) {
             throw new \RuntimeException('Source directory has uncommitted changes');

src/Composer/Downloader/HgDownloader.php

@@ -48,7 +48,6 @@ class HgDownloader extends VcsDownloader
      */
     protected function enforceCleanDirectory($path)
     {
-        $output = array();
         $this->process->execute(sprintf('cd %s && hg st', escapeshellarg($path)), $output);
         if (trim($output)) {
             throw new \RuntimeException('Source directory has uncommitted changes');

src/Composer/Downloader/VcsDownloader.php

@@ -100,4 +100,4 @@ abstract class VcsDownloader implements DownloaderInterface
      * @throws \RuntimeException if the directory is not clean
      */
     abstract protected function enforceCleanDirectory($path);
-}
+}