send-email: relay '-v N' to format-patch

send-email relays unrecognized arguments to its format-patch call.
Passing '-v N' leads to an error because -v is consumed as
send-email's --validate.  For example,

  git send-email -v 3 @{u}

fails with

  fatal: ambiguous argument '3': unknown revision or path not in the
  working tree.  [...]

To prevent this, add the short --reroll-count option to send-email's
main option list and explicitly provide it to the format-patch call.

There other format-patch options that send-email doesn't relay
properly, including at least -n, -N, and the diff option -D.  Punt on
these because dealing with them is more complicated:

 * they would require configuring send-email to not ignore option case

 * send-email makes three GetOptions() calls with different sets of
   options, the last being the main set of options.  Unlike -v, which
   is consumed by the last GetOptions call, the -n, -N, and -D options
   are consumed as abbreviations by the earlier calls.

Signed-off-by: Kyle Meyer <kyle@kyleam.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9001-send-email.sh

@@ -2334,6 +2334,12 @@ test_expect_success $PREREQ 'test that send-email works outside a repo' '
 		"$(pwd)/0001-add-main.patch"
 '
 
+test_expect_success $PREREQ 'send-email relays -v 3 to format-patch' '
+	test_when_finished "rm -f out" &&
+	git send-email --dry-run -v 3 -1 >out &&
+	grep "PATCH v3" out
+'
+
 test_expect_success $PREREQ 'test that sendmail config is rejected' '
 	test_config sendmail.program sendmail &&
 	test_must_fail git send-email \