github wordpress

Hello, I want to know if the following is possible. I have 2 free wordpress plugins on the wordpress plugin directory and i have 2 paid versions of the plugin that users can download from my website. What i want is that the plugins are on github (i already have an account) and that if i make any changes i can direct publish them to wordpress plugin directory Also for the paid plugins i want an option that if a update is available, users can update them from github. Is that possible, and how much is that to set it up? And please tell by bid what needs to be done