Fix string length handling in \SplFileinfo::getBasename()

[m-vo]

Here is an attempt at fixing #8861. I also added some general tests for SplFileInfo::getBasename().

Though I have to admit, that I'm not familiar with the php source at all. So please have a very critical look at this. ☺️

/cc @Girgias

[Girgias]

So... I don't think the fix is totally correct. As this code pattern exists at least in two other places (see: 7cd8879#diff-57114fa464355c4d586b830708e075e98ea0bf0f71e7a29fbe9fbede98e1d4e4R655 and 7cd8879#diff-57114fa464355c4d586b830708e075e98ea0bf0f71e7a29fbe9fbede98e1d4e4R925) which made me try to write some more tests such as:

<?php

echo (new \SplFileInfo('/path/to/a.txt'))->getFilename() . PHP_EOL;
echo (new \SplFileInfo('path/to/b'))->getFilename() . PHP_EOL;
echo (new \SplFileInfo('c.txt'))->getFilename() . PHP_EOL;
echo (new \SplFileInfo('d'))->getFilename() . PHP_EOL;
echo (new \SplFileInfo('~/path/to//e'))->getFilename() . PHP_EOL . PHP_EOL;

?>

Which is also broken by the same commit:

But if I apply the same fix as here I get:

/a.txt
/b
c.txt
d
/e

As an output, so ... yeah

[Girgias]

I don't know how to GitHub so superseeded by #8862

[fritzmg]

superseeded by #8862

You mean #8869 :)