laravel/framework — pull request #5984 by JosephSilber (2014-10-05 21:11:55+00:00)
Title: [4.2] Set morphs directly

```php
$post->images()->create(['path' => 'some/path.jpg']);
```

Currently, creating a new model off a morph relationship does not correctly set the foreign keys unless they're fillable - which I don't think they should be.

This change sets the foreign keys directly on the model, bypassing the fillable filter.