
Marc's implementation would only ever process the include-once urls a single time. This changes that to process them every time, with the second time coming from a file on disk rather than the url. You can then do expiring or one time use URLs in the include-once and have all function of if the content was there every time. The cached file is readable by root-only.
This project is cloud-init it is hosted on launchpad at https://launchpad.net/cloud-init The package was previously named ec2-init.