Description:
------------
If you trying to run a phar file from a directory which path contains ".tar" inside, it fails. 

To reproduce, create a simple phar with the attached test script, and then:
mkdir blah.tar-blah
cp test.phar ./blah.tar-blah/

And try running:
php ./blah.tar-blah/test.phar

The bug is most probably caused by this line: http://lxr.php.net/xref/PHP_5_4/ext/phar/tar.c#116

It's funny that I came across this when one of my colleagues was unable to run 'composer.phar' on our new server. The home directories are using lower-cased "first.last" naming pattern there and the colleague happened to have a last name  starting with Tar :) It took a while to figure out that you can't run Phars if you last name starts with Tar :)

Test script:
---------------
<?php

$phar = new Phar('test.phar');
$phar->addFromString('test.php', '<?php echo "Test";');
$longFile = str_repeat("# just some dummy stuff\n", 500);
$phar->addFromString('some.txt', $longFile);

$stub = <<<'EOF'
#!/usr/bin/env php
<?php

Phar::mapPhar('test.phar');

require 'phar://test.phar/test.php';

__HALT_COMPILER();
EOF;

$phar->setStub($stub);

Expected result:
----------------
"Test" being output

Actual result:
--------------
PHP Fatal error:  Uncaught exception 'PharException' with message 'phar error: "/root/blah.tar-blah/test.phar" is a corrupted tar file (checksum mismatch of file "#!/usr/bin/env php
<?php

Phar::mapPhar('test.phar');

require 'phar://test.phar/test.php';

__HALT_")' in /root/blah.tar-blah/test.phar:4
Stack trace:
#0 /root/blah.tar-blah/test.phar(4): Phar::mapPhar('test.phar')
#1 {main}
  thrown in /root/blah.tar-blah/test.phar on line 4