[PATCH 0/4] Fix -B "very-different" logic.

I am sending the following four patch series:

        [PATCH 1/4] Tweak count-delta interface
        [PATCH 2/4] diff: Fix docs and add -O to diff-helper.
        [PATCH 3/4] diff: Clean up diff_scoreopt_parse().
        [PATCH 4/4] diff: Update -B heuristics.

The first three are preparations and cleanups I found necessary
while I was working on the last one, which is the gem of this
series.  It addresses the concerns you raised in your message
"Careful." while keeping the semantics I wanted to have "if you
keep 97 lines out of original 100-line document, it does not
matter if the end result is a 110-line or 1000-line document.
You did not do a rewrite."

You may have to remove the warning about git-status with this
change, though.