Fix some more diff options changes.

This fixes various problems in the new diff options code.

 - Fix --cc/-c --patch; it showed two-tree diff used internally.

 - Use "---\n" only where it matters -- that is, use it
   immediately after the commit log text when we show a
   commit log and something else before the patch text.

 - Do not output spurious extra "\n"; have an extra newline
   after the commit log text always when we have diff output and
   we are not doing oneline.

 - When running a pickaxe you need to go recursive.

Signed-off-by: Junio C Hamano <junkio@cox.net>