src/Composer/Installer/MetapackageInstaller.php
public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
    {
        if (!$repo->hasPackage($initial)) {
            throw new \InvalidArgumentException('Package is not installed: '.$initial);
        }

        $name = $target->getName();
        $from = $initial->getFullPrettyVersion();
        $to = $target->getFullPrettyVersion();
        $actionName = VersionParser::isUpgrade($initial->getVersion(), $target->getVersion()) ? 'Updating' : 'Downgrading';
        $this->io->writeError("  - " . $actionName . " <info>" . $name . "</info> (<comment>" . $from . "</comment> => <comment>" . $to . "</comment>)");

        $repo->removePackage($initial);
        $repo->addPackage(clone $target);
    }
public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
    {
        if (!$repo->hasPackage($initial)) {
            throw new \InvalidArgumentException('Package is not installed: '.$initial);
        }

        $name = $target->getName();
        $from = $initial->getFullPrettyVersion();
        $to = $target->getFullPrettyVersion();
        $actionName = VersionParser::isUpgrade($initial->getVersion(), $target->getVersion()) ? 'Updating' : 'Downgrading';
        $this->io->writeError("  - " . $actionName . " <info>" . $name . "</info> (<comment>" . $from . "</comment> => <comment>" . $to . "</comment>)");

        $repo->removePackage($initial);
        $repo->addPackage(clone $target);
    }
{@inheritDoc}