The behaviour is following the [docopt](http://docopt.org/) standards.

Assume the following InputDefinition:
````php
new InputDefinition(array(
    new InputOption('foo', 'f'),
    new InputOption('bar', 'b', InputOption::VALUE_REQUIRED),
    new InputOption('cat', 'c', InputOption::VALUE_OPTIONAL),
));
````

The behaviour is:

| Input               | Values                          |
| ------------------- | ------------------------------- |
| `--bar=Hello`       | b = Hello                       |
| `--bar Hello`       | b = Hello                       |
| `-b Hello`          | b = Hello                       |
| `-b=Hello`          | INVALID                         |
| `-bHello`           | b = Hello                       |
| `-fbHello`          | f = true, b = Hello             |
| `-fcHello -b World` | f = true, c = Hello, b = World  |
| `-cfHello -b World` | f = null, c = fHello, b = World |