Merge branch 'mf/format-patch-commit-list-format'

Improve the recently introduced `git format-patch
--commit-list-format` (formerly `--cover-letter-format`) option,
including a new "modern" preset and better CLI ergonomics.

* mf/format-patch-commit-list-format:
  format-patch: --commit-list-format without prefix
  format-patch: add preset for --commit-list-format
  format-patch: wrap generate_commit_list_cover()
  format.commitListFormat: strip meaning from empty
  docs/pretty-formats: add %(count) and %(total)
  format-patch: rename --cover-letter-format option
  format-patch: refactor generate_commit_list_cover
  pretty.c: better die message %(count) and %(total)