Prior to this commit, Vagrants output would only show that a file provisioner was running, but had no detail as to what file was being copied to where. This is especially confusing if a Vagrantfile has multiple file provisioners. This commit updates that by showing the source and destination of the file so that it's clearer what is being copied and to where.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.