patch, 4 partsGenerate cover letters with format-patch

Cover letters are often useful for patch series that don't have a single patch whose message should explain everything. But they're somewhat of a pain to generate by hand, since you have to remember what generated text you want to put in them, how you want to address them, how many patches are in the series, what you're putting in the subject tag, and so forth. This series adds a --cover-letter flag that generates one more message at the start of the series, with all of the sequencing and generation code intact, with a few spaces for you to fill in. This cover letter is an example of the output (without the option to thread the patches).

IIRC, I requested this feature, and Johannes implemented it and sent me a patch, and then I rewrote the patch almost entirely, but I'd never have figured out format-patch without his patch as a guide.

	-Daniel
*This .sig left intentionally blank*

Daniel Barkalow (4):
      Improve message-id generation flow control for format-patch
      Export some email and pretty-printing functions
      Retain extra blank lines between the summary and the body
      Add a --cover-letter option to format-patch

 Documentation/git-format-patch.txt                 |    6 +
 builtin-log.c                                      |  244 ++++++++++++++------
 commit.h                                           |   15 ++
 log-tree.c                                         |  126 ++++++-----
 log-tree.h                                         |    2 +
 pretty.c                                           |   32 ++--
 t/t4013-diff-various.sh                            |    1 +
 ...tch_--stdout_--cover-letter_-n_initial..master^ |  101 ++++++++
 8 files changed, 378 insertions(+), 149 deletions(-)
 create mode 100644 t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^