Merge branch 'ew/mboxrd-format-am'

Teach format-patch and mailsplit (hence "am") how a line that
happens to begin with "From " in the e-mail message is quoted with
">", so that these lines can be restored to their original shape.

* ew/mboxrd-format-am:
  am: support --patch-format=mboxrd
  mailsplit: support unescaping mboxrd messages
  pretty: support "mboxrd" output format

builtin/log.c

@@ -953,7 +953,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	struct pretty_print_context pp = {0};
 	struct commit *head = list[0];
 
-	if (rev->commit_format != CMIT_FMT_EMAIL)
+	if (!cmit_fmt_is_mail(rev->commit_format))
 		die(_("Cover letter needs email format"));
 
 	committer = git_committer_info(0);