bug #2711 FixCommand - fix diff optional value handling (keradus)
bug #2711 FixCommand - fix diff optional value handling (keradus)

This PR was merged into the 2.2 branch.

Discussion
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FixCommand - fix diff optional value handling

regression fix for #2554:
```php
new InputOption('diff', '', InputOption::VALUE_OPTIONAL, 'Also produce diff for each file.', 'sbd'),
```
that means:
- 'diff' option may or may not be passed
- when it's passed, value for it is optional
- 'sbd' is default value of `diff` option regardless it is passed or not (!!!)

I guess assumption during creating 2254 was that `sbd` would be only a value for `diff` if one would pass `--diff` (without value). Apparently, it is a value even if one would not pass that option at all, leading to generate diff even without using `--diff` option.

ref https://github.com/symfony/symfony/issues/11572

Commits
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5546893d FixCommand - fix diff optional value handling

gharlan/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,keradus/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,keradus/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,lucasmichot/PHP-CS-Fixer,Soullivaneuh/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,lucasmichot/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,Soullivaneuh/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer