Make directory mirrors fetch from fallback directory mirrors
This is the parent task for making directory mirrors fetch from fallback directory mirrors. (#15775 (moved) / #4483 (moved) make clients fetch from fallback directory mirrors.)
I think we'll get this done in 0.2.9, if we get it done earlier, great. Clients can start fetching from fallback directory mirrors in 0.2.8 regardless.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information