Merge branch 'jc/send-email-pre-process-fix'

When "git send-email" that uses the validate hook is fed a message
without and then with Message-ID, it failed to auto-assign a unique
Message-ID to the former and instead reused the Message-ID from the
latter, which has been corrected.  This was a fix for a recent
regression caught before the release, so no need to mention it in
the release notes.

* jc/send-email-pre-process-fix:
  t9001: mark the script as no longer leak checker clean
  send-email: clear the $message_id after validation

git-send-email.perl

@@ -1788,6 +1788,7 @@ sub pre_process_file {
 	$subject = $initial_subject;
 	$message = "";
 	$message_num++;
+	undef $message_id;
 	# Retrieve and unfold header fields.
 	my @header_lines = ();
 	while(<$fh>) {