cvsimport: always pass user data to "system" as a list

This avoids invoking the shell. Not only is it faster, but
it prevents the possibility of interpreting our arguments in
the shell.

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

git-cvsimport.perl

@@ -767,7 +767,7 @@ sub commit {
 	waitpid($pid,0);
 	die "Error running git-commit-tree: $?\n" if $?;
 
-	system("git-update-ref $remote/$branch $cid") == 0
+	system('git-update-ref', "$remote/$branch", $cid) == 0
 		or die "Cannot write branch $branch for update: $!\n";
 
 	if ($tag) {