It looks like the "Subversion commit message URLs" section is required, though it is not enforced.

Issue Summary

I was able to set up the configuration in Administer|Settings|Subversion, but when I tried to add a repository under Administer|subversion|repositories, it said "Added Subversion repository: repo" in the log, but no repositories showed up in the list. At first I thought this was because I had not entered values in the "Subversion commit message URLs", because the INSERT query seems to require these fields even though they are not marked as required. I'm not sure what valid values would be for those fields, but I put an URL in there just so the SQL syntax would be correct. It looks like the "Subversion commit message URLs" section is required, though it is not enforced.