File::joinVersion

private function joinVersion()
{
	$lastVersion = $this->getLastVersion();
	if (!$lastVersion)
	{
		return null;
	}

	$joinData = array('CREATE_TIME' => new DateTime);

	if (!$lastVersion->joinData(
		array_merge(
			$joinData,
			$this->getHistoricalData()
		)
	))
	{
		$this->errorCollection->add($lastVersion->getErrors());

		return null;
	}

	if ($this->prevFileId && $this->prevFileId != $this->fileId)
	{
		CFile::delete($this->prevFileId);
	}

	return $lastVersion;
}