-dit(bf(--force)) This option used to alter the behavior of the --delete
-option to force deletion of non-empty directories, but that happens now
-anyway because rsync does deletes in depth-first order. The only known
-difference that --force makes now is an obscure case where the source is a
-non-directory (for example a file or a symlink) but the destination is a
-directory that contains a directory by the same name as the source while
---recursive mode is in effect.
+dit(bf(--force)) This options tells rsync to delete directories even if
+they are not empty when they are to be replaced by non-directories. This
+is only relevant without --delete because deletions are now done depth-first.
+Requires the --recursive option (which is implied by -a) to have any effect.