If I try to find security/tor in https://svnweb.freebsd.org/ports/branches/2017Q3/security/ it's only displayed until ruby-camellia/, not until the tor/ ports.
viewvc seems to split long listings into multiple pages. Note the "Go To:" button near the top of the page. The tor ports are part of the second "page": https://svnweb.freebsd.org/ports/branches/2017Q3/security/?dir_pagestart=1000
Yes, thanks, that's how it works. I missed that button.