Question about rsync -uav dir1/. dir2/.: possib to link?

[L A Walsh]

I noticed in looking at download dirs for a project, that
another mirror had "crept-in" for usage (where different mirrors
are stored under mirror-URL names). To copy over the diffs,
normally I'd do:
   rsync -uav dir1/. dir2/.
 (where dir1="the new mirror that I'd switched
to by accident, and dir2=the original dir).

The files were "smallish" so I just copied them, BUT I wass
wondering if there was an option similar to using 'cp' for
a dircopy, but instead of
   cp -a dr1 dr2
using:
   cp -al dr1 dr2

to just hard-link over files from "dir1" to "dir2" (both
are on the same file system).

I looked at (and tried) --link-dest=DIR
(hardlink to files in DIR when unchanged), but either I had the syntax
wrong, or didn't understand it as it didn't seem to do what I
wanted: cp'ing the new files in dir1 into the orig dir).

Does rsync have an option to just "copy" over the new
files via a hardlink?

Tnx!