merge: fix small bug with a failed merge across a rename If $HGMERGE wasn't able to fix the conflicts, we wouldn't copy f to fd, and util.set_exec wouldn't find the file.

#!/bin/sh
# http://www.selenic.com/mercurial/bts/issue433

hg init a
cd a
echo a > a
hg commit -Ama

hg parents -r 0 doesnotexist
true