Prevents 12 byte limit for magic header

Delta	1 line added, 1 line removed

File.php

		$this->isDir = $mode === '40000' \|\| $mode === '040000';

		- $buffer = $this->isDir ? '' : substr($contents, 0, 12);
		+ $buffer = $this->isDir ? '' : $contents;

		$this->mediaType = MediaTypeSniffer::isMediaType($buffer, $name);