Merge branch 'fc/send-email-annotate'

Allows format-patch --cover-letter to be configurable; the most notable is the "auto" mode to create cover-letter only for multi patch series. * fc/send-email-annotate: rebase-am: explicitly disable cover-letter format-patch: trivial cleanups format-patch: add format.coverLetter configuration variable log: update to OPT_BOOL format-patch: refactor branch name calculation format-patch: improve head calculation for cover-letter send-email: make annotate configurable