How should autoupgrade work?

Autoupgrade is a vital for keeping what Odysseus will have for extensions compatible with the network services they relay on. Sure this could be seen as a universal backdoor, but by keeping it declarative and non-programmable concerned surfers can still see any potential backdoors in it's code.

To implement this at it's most basic we can wrap a session with a cache with infinite storage. For more efficiency for larger files, GGit can be useful. This'll probably require a higher level wrapper that can fetch particular files from a Git repository.

For more complex cases where we decode the data and hand it WebKit, we can drop down to the libsoup message level in order to capture the caching headers and queue up a redownload/reparse.