How-to update codeigniter4 framework via composer?

Hi all,

I installed alpha2 via this command:

composer create-project codeigniter4/framework

(or I think I may have actually used

composer install codeigniter4/framework:dev-master

How do I update to alpha3 using composer? I ran:

composer update

in the framework directory and it only updated:

Package operations: 0 installs, 2 updates, 0 removals
  - Updating sebastian/environment (3.1.0 => 4.0.1): Downloading (100%)
  - Updating phpunit/phpunit (7.4.3 => 7.4.4): Downloading (100%)


I'm new to composer- could someone please tell me the command to update the entire framework from alpha2->alpha3?

Also, I'm concerned my application and public directories will get overridden. Is composer smart enough to leave those alone?

Thanks so much!

-Kyle