Merge branch 'jc/log-p-cc'

"git log --cc" did not show any patch, even though most of the time the user meant "git log --cc -p -m" to see patch output for commits with a single parent, and combined diff for merge commits. The command is taught to DWIM "--cc" (without "--raw" and other forms of output specification) to "--cc -p -m". * jc/log-p-cc: builtin/log.c: minor reformat log: show merge commit when --cc is given log: when --cc is given, default to -p unless told otherwise log: rename "tweak" helpers