Add link to "tree root" (root directory) also for not defined name,
for example for "tree" action without defined "file_name" which means
"tree root".

Add " / " at the end of path when $type eq "tree".
Signed-off-by: NJakub Narebski <jnareb@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>