patch, 2 partsImprove cover letter shortlog generation

This is a somewhat gratuitous cover letter, which I'm mainly including because I did this with "./git format-patch --stdout --cover-letter -n -2". I also just tried -4, and correctly got a shortlog (including a patch out of next) and no diffstat (because the tip of next is a merge, and so there were two boundary commits).

Daniel Barkalow (2):
      Add API access to shortlog
      Improve collection of information for format-patch --cover-letter

 builtin-log.c      |   49 +++++++++--------
 builtin-shortlog.c |  149 ++++++++++++++++++++++++++++------------------------
 shortlog.h         |   26 +++++++++
 3 files changed, 132 insertions(+), 92 deletions(-)
 create mode 100644 shortlog.h