Testdisk made an extended partition end outside of my hard disk, so I fixed it with fixparts. Problem is, I had originally had a bit of space in the beginning of the extended partition. Now it's gone, and GParted wants me to move (read: copy) the entire extended partition (about 500GB) to the left before resizing it by 50GB.
How can I resize an extended (container) partition without moving the whole thing? I am not averse to any command-line utilities. I am running 12.10 in RAM right now.