This plugin adds plugins on activation to a composer.json-file and on deactivation removes them.
That way you can handle your plugins via composer.
Plugins are added to the composer.json via wpackagist which makes the wordpress-plugin-directory available via git.
But you can also manually add plugins to the pluginlist and on activation the plugin is checked for a composer.json file and if one exists the name is used to add the plugin to the composer.json-File.