There's an FS API that shipped yesterday:

    /fs/read?path=X   | GET           | Read file (supports Range headers)           
    /fs/write?path=X  | PUT           | Write file (body = raw bytes)                
    /fs/list?path=X   | GET           | List directory 
    /fs/delete?path=X | DELETE/POST   | Delete files/dirs                            
    /fs/rename        | POST          | Rename/move                                  
    /fs/copy          | POST          | Copy files/dirs                              
    /fs/chmod         | POST          | Change permissions                           
    /fs/chown         | POST          | Change ownership                             
    /fs/watch         | GET (WebSock) | Watch for filesystem changes                 

But I've just been using magic-wormhole for this.