The "--cc" option to "git log" is clearly a request to show some
sort of combined diff (be it --patch or --raw), but traditionally
we required the command line to explicitly ask for "git log -p --cc".
Teach the command line parser to treat a lone "--cc" as if the user
specified "-p --cc". Formats that do ask for other forms of diff
output, e.g. "log --raw --cc", are not overriden.