When symlinks are encountered, the item that they point to (the referent) is copied, rather than
the symlink. In older versions of rsync, this option also had the side-effect of telling the
receiving side to follow symlinks, such as symlinks to directories. In a modern rsync such as
this one, you’ll need to specify --keep-dirlinks (-K) to get this extra behavior. The only
exception is when sending files to an rsync that is too old to understand -K -- in that case, the
-L option will still have the side-effect of -K on that older receiving rsync.
This is equivalent to -rlptgoD. It is a quick way of saying you want recursion and want to
preserve almost everything (with -H being a notable omission). The only exception to the above
equivalence is when --files-from is specified, in which case -r is not implied.
Note that -a does not preserve hardlinks, because finding multiply-linked files is expensive. You
must separately specify -H.