The problem seems to be that the "fossil diff" command ignores whitespace
at the end of lines.  IIRC, I added this "feature" when I encountered some
check-ins from people using windows editors that inserted \r at the end of
every line.  If end-of-line whitespace is not ignored in that case, then
the diff output is useless.

Maybe the right solution is to make "diff" output ignore end-of-line
whitespace but create a new command for generating patches that takes
end-of-line whitespace into account?