Merge branch 'mf/format-patch-cover-letter-format' into next

Merge branch 'mf/format-patch-cover-letter-format' into next

"git format-patch --cover-letter" learns to use a simpler format
instead of the traditional shortlog format to list its commits with
a new --cover-letter-format option and format.commitListFormat
configuration variable.

* mf/format-patch-cover-letter-format:
  docs: add usage for the cover-letter fmt feature
  format-patch: add commitListFormat config
  format-patch: add ability to use alt cover format
  format-patch: move cover letter summary generation
  pretty.c: add %(count) and %(total) placeholders