Merge branch 'jc/log-p-cc'

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