prop140 / compression: Unified directory cache backend
With prop140 and/or ahf's compression proposal, we'll need to cache more documents than previously, to include multiple consensuses, diffs, compressed consensuses, etc. We could do this in an ad-hoc way, but we'll probably be better off with a real abstraction here.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information