src/Composer/Installer/PearInstaller.php
public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
    {
        $this->uninstall($repo, $initial);
        $this->install($repo, $target);
    }
public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
    {
        $this->uninstall($repo, $initial);
        $this->install($repo, $target);
    }
{@inheritDoc}