Directory of command handlers (e.g. "store"; "add" -> Store.handle_add)
"store"; "add"
A handler for a command, accepting options of type 'a
'a
Parse the options and run the appropriate handler.
Get the help text for this command. None if this is a hidden (internal) command.
Get the list of options supported by this command. For tab-completion.
Return the supported option names as a set (for tab-completion).