@phillh.noumea
Thanks for showing me the "hack" regarding Move, then click Stop.
I can't think of any way to describe that mangled mess other than to call it a hack.
But imagine this. You have two hard drives that you want to keep syncronized. Your internal and external drive each have 4,000 photos on them (because you use your external as a backup). But you have taken some more photos (another 250 which equals 4,250 total) and they are on your internal drive. You want to put them on the external. You'd like to do what every other version of OS X did -- Grab them all and copy them to drive #2, but tell Finder not to copy duplicates. Now you are only copying 250 files over, and it would be a fairly short process. But alas, this won't work in Apple's latest OS...
So far as I can tell, here's what you have to do.
#1 Go to your external drive.
#2 Delete every photo (4,000) on you external drive.
#3 Copy 4,250 photos from your internal drive to your external drive.
#4 Go to the grocery store and run errands
Meanwhile you are opening yourself up to disaster because for a period of time you only have one copy.
Another work-around is to let Finder copy the duplicates. So now you have 4,250 + 4,000 = 8,250 files on your external drive.
Nice.
Way to go Apple.
This dumbing down of the PC operating system is going waaaaay too far.
I wonder if Finder alternatives (like PathFinder) restore the lost functionality?