Markdown link error on link url has sha1 like string.

Created by: harryxu

GL version 3.1

[text](http://xxx.com/myproject/tree/8fd7ffd0f440eb4cabef30d546bbba6b82991f15/a.php) 

This will produce:

<a href="http://xxx.com/myproject/tree/&lt;a href=" />text</a>

not

<a href="http://xxx.com/myproject/tree/8fd7ffd0f440eb4cabef30d546bbba6b82991f15/a.php">text</a>