Force Composer to update a package

You have created all meta data about your package yourself, likely making Composer think that the data didn't change.

The easier, and probably working, way would be to simply point to the repository URL and let Composer query the meta data from the composer.json file contained in the repository:

"repositories": [{
    "type": "vcs",
    "url": "https://github.com/myrepo/MyExtension.git"
}]

For it to update your changes you need to version your package but as you said earlier you are not versioning your packages so for it to update your changes you can go to composer.lock to remove your package entry or to use composer to remove the package and install it again. eg

 // composer remove vendor/package && composer require vendor/package
 composer remove zizaco/entrust && composer require zizaco/entrust