Optional interfaces are becoming more important in rclone,
--track-renames and --backup-dir both rely on them.
Up to this point rclone has used interface upgrades to define optional
behaviour on Fs objects. However when one Fs object wraps another it
is very difficult for this scheme to work accurately. rclone has
relied on specific error messages being returned when the interface
isn't supported - this is unsatisfactory because it means you have to
call the interface to see whether it is supported.
This change enables accurate detection of optional interfaces by use
of a Features struct as returned by an obligatory Fs.Features()
method. The Features struct contains flags and function pointers
which can be tested against nil to see whether they can be used.
As a result crypt and hubic can accurately reflect the capabilities of
the underlying Fs they are wrapping.
If remote:path points to a file make NewFs return a sentinel error
fs.ErrorIsFile and an Fs which points to the parent.
Use this to remove the LimitedFs and just add this file to the
--files-from list.
This means that server side operations can be used also.
Fixes#518Fixes#545
This will allow setting up a remote with copy&paste of values to a headless machine. It will allow copy+pasting a token into the configuration.
This requires rclone to be on a machine with a proper browser. Custom client id and secrets are supported.
To test token generation, use `rclone auth "fs type"`.
