is there any way to easily update a plugin installed on multiple sites from a github repo. I know I can do it from the command line of each server using git pull. but is there a way to do it from the wordpress admin similar to how plugins are updated?
I wrote a PHP class that allows a plugin developer to incorporate updates from GitHub within their plugin. Here's a link for it -> https://github.com/jkudish/WordPress-GitHub-Plugin-Updater
Check out this plugin updater class for WordPress: https://github.com/jkudish/WordPress-GitHub-Plugin-Updater
I recently wrote up a post about deploying an entire WordPress site with a few custom plugins and theme to multiple servers using Capistrano. You could probably do the same for just the single plugin repo.
There's a bunch of good posts out there for the step-by-step details on getting Capistrano going for WordPress.
I used this plugin
It works fine,
Supports github, gitlab, bitbucket
Free for public repositories