I updated to Cap 3 and it appears that set :deploy_via, :copy
is no longer supported. In the release annoucement there is a link to a video for replicating the copy
I ran into the same issue and posted a similar question on the capistrano google group.
See here: https://groups.google.com/forum/#!topic/capistrano/BRa4Vj1_mEo
Short answer: Write your own rake task.
The capistrano maintainer provided some example code, via a blog post on his website, that can be found here: http://lee.hambley.name/2013/06/11/using-capistrano-v3-with-chef.html
In the end, we've decided to go w/ a different strategy entirely, and implement a mirror repository on the same network as our servers.