Allows rclone sync to accept the same output file flags as rclone check,
for the purpose of writing results to a file.
A new --dest-after option is also supported, which writes a list file using
the same ListFormat flags as lsf (including customizable options for hash,
modtime, etc.) Conceptually it is similar to rsync's --itemize-changes, but
not identical -- it should output an accurate list of what will be on the
destination after the sync.
Note that it has a few limitations, and certain scenarios
are not currently supported:
--max-duration / CutoffModeHard
--compare-dest / --copy-dest (because equal() is called multiple times for the
same file)
server-side moves of an entire dir at once (because we never get the individual
file objects in the dir)
High-level retries, because there would be dupes
Possibly some error scenarios that didn't come up on the tests
Note also that each file is logged during the sync, as opposed to after, so it
is most useful as a predictor of what SHOULD happen to each file
(which may or may not match what actually DID.)
Only rclone sync is currently supported -- support for copy and move may be
added in the future.
