gpg-interface: handle missing " with " gracefully in parse_ssh_output()
If the output of ssh-keygen starts with "Good \"git\" signature for ",
but is not followed by " with " for some reason, then parse_ssh_output()
uses -1 as the len parameter of xmemdupz(), which in turn will end the
program. Reject the signature and carry on instead in that case.
Signed-off-by: René Scharfe <l.s.r@web.de> Acked-by: Fabian Stelzer <fs@gigacodes.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>