A little over two years ago I wrote:
The magic option is -T / –temp-dir
It turns out that this is true, but not enough. You also need –delay-updates, and you must create the tempdir first. So, something like:
ssh user@host mkdir /what/ever.tmp rsync --delay-updates --temp-dir /what/ever.tmp file user@host:/what/ever/ ssh user@host rmdir /what/ever.tmp