My client has asked me to make a WordPress Plugin that people must purchase. Therefore, it is not put into the WordPress.org plugin repository and is not updatable by default from the Plugins menu in wp-admin.
Is there a best practice way for making the plugin updatable? As in, showing an update on the dashboard, plugin options panel, and Plugins page. When clicked, it automatically upgrades the source code without one having to go through a series of steps. How would you suggest this would work, and do you have any code snippets to explain the process?
I think the best code snippets are in the WordPress code itself. See how they do it, and duplicate it with your plugin. Basically, they send some information about your installed themes and plugins to an server, which responds back with updates if there are any. You can remove your plugin from the list that is sent to WordPress if you want to keep this info to yourself.