Use git caching to speed build times
It appears we are using S3 caching for software artifacts but not necessarily git caching to speed builds:
http://www.rubydoc.info/github/opscode/omnibus/Omnibus/Config#use_s3_caching-instance_method
For our full releases, we may still opt to do full rebuilds without git caching. But for quick branch deploys, we may want to use git caching.