[chef] Deploy from github, using individual keys

[Mike < >]

I feel like this has been done, demonstrated, but I couldn't find
anything on it.

Flow:

Provision a box
At some point in the run, pull a branch from github (master, tag, etc)
Restart service if changed

By using a GitHub deploy key, I can automate this for prod, sure.

But if I'm using Vagrant, and I want to restrict access to the deploy
key, is there a known way for me to specify "use a user's ssh-agent
forwarded ssh key instead".

Ideas, blogs, thoughts?
-M