Work around a wdiff(1) issue

When the first line is deleted, it appears like this:

[-Use wdiff output to gather the positions, since it's more correct.-]call wdiff on the two buffers, get the output, scan for,

We expect it like this:

[-Use wdiff output to gather the positions, since it's more correct.-]
call wdiff on the two buffers, get the output, scan for,