-MPc
is shortened way for -M -P -c
which is shortened for --metadata --progress --checksum
. Maybe it is good idea to avoid shortened flags in documentation for sake of clarity.
-M, --metadata If set, preserve metadata when copying objects
-P, --progress Show progress during transfer
-c, --checksum Check for changes with size & checksum (if available, or fallback to size only).
All explained in docs.
To quickly find some short flag reference use:
$ rclone help flags | grep "\-P,"
-P, --progress Show progress during transfer
Then you can find --progress in docs for more detailed explanation.