Added note: working copy changes (e.g., deleted vendor folder) should be...

Added note: working copy changes (e.g., deleted vendor folder) should be stashed before beginning the update process. We should probably include this notice on all update guides.

[ci skip]

doc/update/6.x-or-7.x-to-7.14.md

@@ -14,6 +14,12 @@ possible to edit the label text and color. The characters `?`, `&` and `,` are
 no longer allowed however so those will be removed from your tags during the
 database migrations for GitLab 7.2.
+## Stash changes
+
+If you [deleted the vendors folder during your original installation](https://github.com/gitlabhq/gitlabhq/issues/4883#issuecomment-31108431), [you will get an error](https://gitlab.com/gitlab-org/gitlab-ce/issues/1494) when you attempt to rebuild the assets in step 7. To avoid this, stash the changes in your GitLab working copy before starting:
+
+    git stash
+
 ## 0. Stop server
     sudo service gitlab stop