The Master Zend Framework site has continued their series covering Composer and some more advanced concepts than just the usual introduction. In this new tutorial Matthew Setter shows you how to work with forked repositories.
Have you ever submitted a patch to a repository which your application relies on, but, because that patch is vital to the uptime of your application, you can’t wait for it to be reviewed and merged into the next release?
In times like these, it’s fair to want them to move faster than they normally would, so that you don’t have to wait for the normal review, merge, and release cycles. [...] But, you may urgently need the patch to be applied and released. So, what do you do? In times like these, you can use Composer’s ability to use custom repositories, specifically a fork which you create and patch.
If this sounds appealing to you — because perhaps you’re in this very situation right now — let’s now step through the process of modifying your composer.json configuration so that you can use one.
He walks through the Composer configuration you'll need to update to work with the forked repository as you'd expect. He also covers changes that would need to be made for working with private repositories and using local files instead of remote.