[Legogris]

They have been working on this and you can actually do it today even if it's not very well documented (again, haven't tried myself):

  $ keybase fs sync --help
  NAME:
   keybase fs sync - Manages the per-folder syncing state

  USAGE:
   keybase fs sync <command> [arguments...]

  COMMANDS:
   enable       syncs the given folder to local storage, for offline access
   disable      Stops syncing the given folder to local storage
   show         shows the sync configuration and status for the given folder, or all folders if none is specified
   help, h      Shows a list of commands or help for one command

[eropple]

Interesting - I haven't seen this before. Thanks, that's awesome.