mitchellh/vagrant — pull request #2800 by miketheman (2014-01-10 17:43:24+00:00)
Title: extend Virtualbox convenince methods

In the vein of #2426, I too can never remember syntax, and end up
hunting for either an existing Vagrantfile or starting to dig up
details.

This does bring up the question of potentially looking at cross-provider-specific methods for customization - but that's possibly a slippery slope.