src/Composer/Installer/InstallationManager.php
public function install(RepositoryInterface $repo, InstallOperation $operation)
    {
        $package = $operation->getPackage();
        $installer = $this->getInstaller($package->getType());
        $installer->install($repo, $package);
        $this->markForNotification($package);
    }
public function install(RepositoryInterface $repo, InstallOperation $operation)
    {
        $package = $operation->getPackage();
        $installer = $this->getInstaller($package->getType());
        $installer->install($repo, $package);
        $this->markForNotification($package);
    }
Executes install operation.

@param RepositoryInterface $repo      repository in which to check
@param InstallOperation    $operation operation instance