Read-only sync (pin IPNS address)

[TheDiscordian]

Currently we effectively have write-only sync, we'll write anything from the filesystem, and sync that to IPFS. A read-only sync could be cool too, where we take an IPNS address, keep the IPFS CID it points to pinned, and map it to MFS using a supplied name.

[TheDiscordian]

Make it so the user can select what files/subdirectories they sync. For example, ["/"] would sync everything, but ["/subdir", "/icon.png"], would sync a subdirectory and a file of the IPNS addr.