Not wrong, but since you’re mentioning vim in the context of git, might be worth adding :cq as a way to exit with a non-zero status to prevent git from finishing the commit / operation.
((cd /tmp/t; find . -type f -print) | sort | while read f; do cmp -s {/tmp/t,/tmp/t1}/$f || vim -f -d {/tmp/t,/tmp/x1}/$f 0<&9 || break; done) 9<&0
Typing ^C to vim doesn't get you very far, so if you make a mistake causing the loop to return 1000's of files you are in for a bit of pain without :cq. The :cq triggers the break, exiting the loop.