Laravel Forge Issue

I am using Laravel Forge and Digital Ocean which has been great.

When I make changes and deploy all works fine, until I add a new package with Composer, I get the below error and It will not deploy after this point?

Wed Jun 15 12:03:12 BST 2016
Warning: Permanently added the RSA host key for IP address '192.30.252.120' to the list of known hosts.
From github.com:********/****
    * branch            master     -> FETCH_HEAD
      08f475b..5802179  master     -> origin/master
   error: Your local changes to the following files would be overwritten by merge:
    vendor/composer/autoload_classmap.php
    vendor/composer/autoload_namespaces.php
    vendor/composer/installed.json
Please, commit your changes or stash them before you can merge.
Aborting
Updating e20816a..5802179

The only way that I can fix is to delete the server and restart. I am using Source Tree to push changes to Git.