disable prepend option on install

src/Composer/Autoload/AutoloadGenerator.php

@@ -37,7 +37,7 @@ class AutoloadGenerator
         $this->eventDispatcher = $eventDispatcher;
     }
 
-    public function dump(Config $config, InstalledRepositoryInterface $localRepo, PackageInterface $mainPackage, InstallationManager $installationManager, $targetDir, $scanPsr0Packages = false, $suffix = '')
+    public function dump(Config $config, InstalledRepositoryInterface $localRepo, PackageInterface $mainPackage, InstallationManager $installationManager, $targetDir, $scanPsr0Packages = false, $suffix = '', $prepend = 'true')
     {
         $this->eventDispatcher->dispatchScript(ScriptEvents::PRE_AUTOLOAD_DUMP);
 
@@ -180,7 +180,7 @@ EOF;
             file_put_contents($targetDir.'/autoload_files.php', $includeFilesFile);
         }
         file_put_contents($vendorPath.'/autoload.php', $this->getAutoloadFile($vendorPathToTargetDirCode, $suffix));
-        file_put_contents($targetDir.'/autoload_real.php', $this->getAutoloadRealFile(true, true, (bool) $includePathFile, $targetDirLoader, (bool) $includeFilesFile, $vendorPathCode, $appBaseDirCode, $suffix, $useGlobalIncludePath));
+        file_put_contents($targetDir.'/autoload_real.php', $this->getAutoloadRealFile(true, true, (bool) $includePathFile, $targetDirLoader, (bool) $includeFilesFile, $vendorPathCode, $appBaseDirCode, $suffix, $useGlobalIncludePath, $prepend));
 
         // use stream_copy_to_stream instead of copy
         // to work around https://bugs.php.net/bug.php?id=64634
@@ -364,7 +364,7 @@ return ComposerAutoloaderInit$suffix::getLoader();
 AUTOLOAD;
     }
 
-    protected function getAutoloadRealFile($usePSR0, $useClassMap, $useIncludePath, $targetDirLoader, $useIncludeFiles, $vendorPathCode, $appBaseDirCode, $suffix, $useGlobalIncludePath)
+    protected function getAutoloadRealFile($usePSR0, $useClassMap, $useIncludePath, $targetDirLoader, $useIncludeFiles, $vendorPathCode, $appBaseDirCode, $suffix, $useGlobalIncludePath, $prepend)
     {
         // TODO the class ComposerAutoloaderInit should be revert to a closure
         // when APC has been fixed:
@@ -395,7 +395,7 @@ class ComposerAutoloaderInit$suffix
             return self::\$loader;
         }
 
-        spl_autoload_register(array('ComposerAutoloaderInit$suffix', 'loadClassLoader'), true, true);
+        spl_autoload_register(array('ComposerAutoloaderInit$suffix', 'loadClassLoader'), true, $prepend);
         self::\$loader = \$loader = new \\Composer\\Autoload\\ClassLoader();
         spl_autoload_unregister(array('ComposerAutoloaderInit$suffix', 'loadClassLoader'));
 
@@ -454,7 +454,7 @@ REGISTER_AUTOLOAD;
         }
 
         $file .= <<<REGISTER_LOADER
-        \$loader->register(true);
+        \$loader->register($prepend);
 
 
 REGISTER_LOADER;

src/Composer/Command/InstallCommand.php

@@ -43,7 +43,8 @@ class InstallCommand extends Command
                 new InputOption('no-scripts', null, InputOption::VALUE_NONE, 'Skips the execution of all scripts defined in composer.json file.'),
                 new InputOption('no-progress', null, InputOption::VALUE_NONE, 'Do not output download progress.'),
                 new InputOption('verbose', 'v|vv|vvv', InputOption::VALUE_NONE, 'Shows more details including new commits pulled in when updating packages.'),
-                new InputOption('optimize-autoloader', 'o', InputOption::VALUE_NONE, 'Optimize autoloader during autoloader dump')
+                new InputOption('optimize-autoloader', 'o', InputOption::VALUE_NONE, 'Optimize autoloader during autoloader dump'),
+                new InputOption('no-prepend', null, InputOption::VALUE_NONE, 'Disables the prepending of the autoloader')
             ))
             ->setHelp(<<<EOT
 The <info>install</info> command reads the composer.lock file from
@@ -101,6 +102,7 @@ EOT
             ->setDevMode(!$input->getOption('no-dev'))
             ->setRunScripts(!$input->getOption('no-scripts'))
             ->setOptimizeAutoloader($input->getOption('optimize-autoloader'))
+            ->setPrepend(!$input->getOption('no-prepend'))
         ;
 
         if ($input->getOption('no-plugins')) {

src/Composer/Installer.php

@@ -106,6 +106,7 @@ class Installer
     protected $update = false;
     protected $runScripts = true;
     protected $updateWhitelist = null;
+    protected $prepend = 'true';
 
     /**
      * @var array
@@ -280,7 +281,7 @@ class Installer
 
             // write autoloader
             $this->io->write('<info>Generating autoload files</info>');
-            $this->autoloadGenerator->dump($this->config, $localRepo, $this->package, $this->installationManager, 'composer', $this->optimizeAutoloader);
+            $this->autoloadGenerator->dump($this->config, $localRepo, $this->package, $this->installationManager, 'composer', $this->optimizeAutoloader, '', $this->prepend);
 
             if ($this->runScripts) {
                 // dispatch post event
@@ -1055,6 +1056,18 @@ class Installer
         return $this;
     }
 
+    /**
+     * Generate autoload_real with/without prepend
+     *
+     * @param  boolean     $prepend
+     * @return Installer
+     */
+    public function setPrepend($prepend = true)
+    {
+        $this->prepend = (boolean) $prepend === true ? 'true' : 'false';
+        return $this;
+    }
+
     /**
      * Disables plugins.
      *