code: public function doUpdate(PackageInterface $initial, PackageInterface $target, $path, $url)
      {
          SvnUtil::cleanEnv();
          $ref = $target->getSourceReference();
  
          if (!$this->hasMetadataRepository($path)) {
              throw new \RuntimeException('The .svn directory is missing from '.$path.', see https://getcomposer.org/commit-deps for more information');
          }
  
          $util = new SvnUtil($url, $this->io, $this->config);
          $flags = "";
          if (version_compare($util->binaryVersion(), '1.7.0', '>=')) {
              $flags .= ' --ignore-ancestry';
          }
  
          $this->io->writeError(" Checking out " . $ref);
          $this->execute($url, "svn switch" . $flags, sprintf("%s/%s", $url, $ref), $path);
      }
docs: {@inheritDoc}