On Mac OSX it's often the case that the command line utilities and other programs that it ships with are incredibly outdated. This includes rsync, a utility in extremely common use to synchronize files between computers.
Even on El Capitan, the version of rsync being used is 2.6.9, which is quickly approaching 10 years in age. As you might image, there's been a lot of development in the last 10 years bringing a whole host of improvements. Thankfully, with Homebrew it's very easy to get up and going with a new version of rsync.
Simply execute the following two commands and you'll bet set to go!
brew tap homebrew/dupes brew install rsync
You'll likely have to restart your terminal for the new binary to be correctly found, but after that you can get going with the new features and improved performance.