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
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i