core-bundle/src/Resources/contao/library/Contao/Folder.php
public function unsynchronize()
	{
		if (!file_exists($this->strRootDir . '/' . $this->strFolder . '/.nosync'))
		{
			System::getContainer()->get('filesystem')->touch($this->strRootDir . '/' . $this->strFolder . '/.nosync');
		}
	}
public function unsynchronize()
	{
		if (!file_exists($this->strRootDir . '/' . $this->strFolder . '/.nosync'))
		{
			System::getContainer()->get('filesystem')->touch($this->strRootDir . '/' . $this->strFolder . '/.nosync');
		}
	}
Unsynchronize the folder by adding a .nosync file