Implement --size-only flag to sync on size not checksum & modtime - fixes #75

docs/content/docs.md

@@ -124,6 +124,7 @@ This help.
       --log-file="": Log everything to this file
       --modify-window=1ns: Max time diff to be considered the same
   -q, --quiet=false: Print as little stuff as possible
+      --size-only=false: Skip based on size only, not mod-time or checksum
       --stats=1m0s: Interval to print stats (0 to disable)
       --timeout=5m0s: IO idle timeout
       --transfers=4: Number of file transfers to run in parallel.

docs/content/dropbox.md

@@ -84,3 +84,10 @@ Dropbox datastores are limited to 100,000 rows so this is the maximum
 number of files rclone can manage on Dropbox.
 
 Dropbox is case sensitive which can sometimes cause duplicated files.
+
+If you use the desktop sync tool and rclone on the same files then the
+md5sums and modification times may get out of sync as far as rclone is
+concerned.  This will cause `Corrupted on transfer: md5sums differ`
+error message when fetching files.  You can work around this by using
+the `--size-only` flag to ignore the md5sums and modification times
+for these files.