Internal function apply_line() is called to copy both context lines
and added lines to the output buffer, while possibly fixing the
whitespace breakages depending on --whitespace=strip settings.
However, it did its fix-up on both context lines and added lines.
This resulted in two symptoms:
(1) The number of lines reported to have been fixed up included
these context lines.
(2) However, the lines actually shown were limited to the added
lines that had whitespace breakages.