format-patch: wrap email addresses after long names

format-patch: wrap email addresses after long names

We already wrap names in "from" headers, which tend to be
the long part of an address. But it's also possible for a
long name to not be wrapped, but to make us want to wrap the
email address. For example (imagine for the sake of
readability we want to wrap at 50 characters instead of 78):

  From: this is my really long git name <foo@example.com>

The name does not overflow the line, but the name and email
together do. So we would rather see:

  From: this is my really long git name
    <git@example.com>

Because we wrap the name separately during add_rfc2047, we
neglected this case. Instead, we should see how long the
final line of the wrapped name ended up, and decide whether
or not to wrap based on that. We can't break the address
into multiple parts, so we either leave it with the name, or
put it by itself on a line.

Test by Erik Faye-Lund.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>