Fix up git downloader and git driver commands

src/Composer/Downloader/GitDownloader.php

@@ -45,7 +45,7 @@ class GitDownloader extends VcsDownloader
         $ref = escapeshellarg($target->getSourceReference());
         $path = escapeshellarg($path);
         $this->io->write("    Checking out ".$target->getSourceReference());
-        $command = 'cd %s && git remote set-url origin %s && git fetch --tags origin && git checkout %3$s && git reset --hard %3$s';
+        $command = 'cd %s && git remote set-url origin %s && git fetch origin && git fetch --tags origin && git checkout %3$s && git reset --hard %3$s';
 
         $commandCallable = function($url) use ($ref, $path, $command) {
             return sprintf($command, $path, $url, $ref);

src/Composer/Repository/Vcs/GitDriver.php

@@ -45,7 +45,7 @@ class GitDriver extends VcsDriver
 
             // update the repo if it is a valid git repository
             if (is_dir($this->repoDir) && 0 === $this->process->execute('git remote', $output, $this->repoDir)) {
-                $this->process->execute('git remote update', $output, $this->repoDir);
+                $this->process->execute('git remote update --prune origin', $output, $this->repoDir);
             } else {
                 // clean up directory and do a fresh clone into it
                 $fs = new Filesystem();

tests/Composer/Test/Downloader/GitDownloaderTest.php

@@ -139,7 +139,7 @@ class GitDownloaderTest extends \PHPUnit_Framework_TestCase
 
     public function testUpdate()
     {
-        $expectedGitUpdateCommand = $this->getCmd("cd 'composerPath' && git remote set-url origin 'git://github.com/composer/composer' && git fetch --tags origin && git checkout 'ref' && git reset --hard 'ref'");
+        $expectedGitUpdateCommand = $this->getCmd("cd 'composerPath' && git remote set-url origin 'git://github.com/composer/composer' && git fetch origin && git fetch --tags origin && git checkout 'ref' && git reset --hard 'ref'");
         $expectedGitResetCommand = $this->getCmd("cd 'composerPath' && git status --porcelain");
 
         $packageMock = $this->getMock('Composer\Package\PackageInterface');
@@ -168,7 +168,7 @@ class GitDownloaderTest extends \PHPUnit_Framework_TestCase
      */
     public function testUpdateThrowsRuntimeExceptionIfGitCommandFails()
     {
-        $expectedGitUpdateCommand = $this->getCmd("cd 'composerPath' && git remote set-url origin 'git://github.com/composer/composer' && git fetch --tags origin && git checkout 'ref' && git reset --hard 'ref'");
+        $expectedGitUpdateCommand = $this->getCmd("cd 'composerPath' && git remote set-url origin 'git://github.com/composer/composer' && git fetch origin && git fetch --tags origin && git checkout 'ref' && git reset --hard 'ref'");
         $expectedGitResetCommand = $this->getCmd("cd 'composerPath' && git status --porcelain");
 
         $packageMock = $this->getMock('Composer\Package\PackageInterface');