This is useful if there are duplicates. Assuming the remote delivers
the entries in a consistent order, this will give the best user
experience in syncing as it will consistently use the first entry for
the sync comparison.
This simplifies the implementation of remotes. The only required
interface is now `List` which is a simple one level directory list.
Optionally remotes may implement `ListR` if they have an efficient way
of doing a recursive list.
This is a fix left over from the v2 conversion. Dropbox ignores the
client modification on an incoming file if it was identical to the
existing file. This change deletes the existing file first before
re-uploading the new one.
* Add options to Put, PutUnchecked and Update for all Fses
* Use these to create HashOption
* Implement this in local
* Pass the option in fs.Copy
This has the effect that we only calculate hashes we need to in the
local Fs which speeds up transfers significantly.
* add support to hashing module
* add dbhashsum to list the hashes
* add support to dropbox module
This means objects up and downloaded to/from Dropbox will have their
hashes checked.
Note after this change local objects are calculating MD5, SHA1 and
DBHASH which is excessive and needs to be fixed.
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.
