+Beginning with rsync 3.0.0, the recursive algorithm used is now an
+incremental scan that uses much less memory than before and begins the
+transfer after the scanning of the first few directories have been
+completed. This incremental scan only affects our recursion algorithm, and
+does not change a non-recursive transfer (e.g. when using a fully-specified
+bf(--files-from) list). It is also only possible when both ends of the
+transfer are at least version 3.0.0.
+
+Some options require rsync to know the full file list, so these options
+disable the incremental recusion mode. These include: bf(--delete-before),
+bf(--delete-after), bf(--delay-updates), and (currently) bf(--hard-links).
+Because of this, the default delete mode when you specify bf(--delete) is now
+bf(--delete-during) (when both ends of the connection are at least 3.0.0;
+use bf(--del) or bf(--delete-during) to request this improved deletion mode
+explicitly). See also the bf(--delete-delay) option that is a better choice
+than using bf(--delete-after).
+