+ - Implemented a new algorithm for hard-link handling that speeds up
+ the code significantly. (J.W. Schultz and Wayne Davison)
+
+ - The --hard-link option now uses the first existing file in the
+ group of linked files as the basis for the transfer. This
+ prevents the sub-optimal transfer of a file's data when a new
+ hardlink is added on the sending side and it sorts alphabetically
+ earlier in the list than the files that are already present on the
+ receiving side.
+
+ - Dropped support for protocol versions less than 20 (2.3.0 released
+ 15 Mar 1999) and activated warnings for protocols less than 25
+ (2.5.0 released 23 Aug 2001). (Wayne Davison and J.W. Schultz,
+ severally)
+
+ - More optimal data transmission for --hard-links (protocol 28).
+
+ - More optimal data transmission for --checksum (protocol 28).
+
+ - Less memory is used when --checksum is specified.
+
+ - Less memory is used in the file list (a per-file savings).
+
+ - The generator is now better about not modifying the file list
+ during the transfer in order to avoid a copy-on-write memory
+ bifurcation (on systems where fork() uses shared memory).
+ Previously, rsync's shared memory would slowly become unshared,
+ resulting in real memory usage nearly doubling on the receiving
+ side by the end of the transfer. Now, as long as permissions
+ are being preserved, the shared memory should remain that way
+ for the entire transfer.
+
+ - Changed hardlink info and file_struct + strings to use allocation
+ pools. This reduces memory use for large file-sets and permits
+ freeing memory to the OS. (J.W. Schultz)
+
+ - The 2 pipes used between the receiver and generator processes
+ (which are forked on the same machine) were reduced to 1 pipe and
+ the protocol improved so that (1) it is now impossible to have the
+ "redo" pipe fill up and hang rsync, and (2) trailing messages from
+ the receiver don't get lost on their way through the generator
+ over to the sender (which mainly affected hard-link messages and
+ verbose --stats output).
+
+ - Improved the internal uid/gid code to be more portable and a
+ little more optimized.
+
+ - The device numbers sent when using --devices are now sent as
+ separate major/minor values with 32-bit accuracy (protocol 28).
+ Previously, the copied devices were sent as a single 32-bit
+ number. This will make inter-operation of 64-bit binaries more
+ compatible with their 32-bit brethren (with both ends of the
+ connection are using protocol 28). Note that optimizations in the
+ binary protocol for sending the device numbers often results in
+ fewer bytes being used than before, even though more precision is
+ now available.
+
+ - Some cleanup of the exclude/include structures and its code made
+ things clearer (internally), simpler, and more efficient.
+
+ - The reading & writing of the file-list in batch-mode is now
+ handled by the same code that sends & receives the list over the
+ wire. This makes it much easier to maintain. (Note that the
+ batch code is still considered to be experimental.)