Description:
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If you use Phar::mount to mount a directory, is_dir() will return false for the mounted directory.

Using PHP 5.3.0 final.

Reproduce code:
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Stub contains:

Phar::interceptFileFuncs();
Phar::mount('albums/', '/home/nibbler/public_html/phar/data/albums/');

Application contains:

var_dump(is_dir('albums'));

Expected result:
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returns true

Actual result:
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returns false