Using "%teamcity.build.branch%" with multiple VCS roots.

I need to have a build configuration that has multiple VCS roots (only 2 in this case) that will each be configured to "Use tags as branches", and will build upon commit from any VCS root.  During the build step, I am creating an Octopus package with "%teamcity.build.branch%" as part of the package name.  With a single VCS root, this variable will contain the tag name, and thus create a nuget package that is easily used in the Octopus Channels.

The problem I'm running into is that, when I add any additional VCS roots, that variable ends up becoming "<Default>", which obviously doesn't work for me at all.

The only solution I can see is to create a new build configuration for every project we have (a lot.  less than 100, but more than just a few).  That is not a viable solution, and I can't imagine that there isn't some other variable that can provide the tag/branch of the VCS root that triggered the build.

I've also tried specifying multiple tags in a single VCS root.  If I leave the "Default branch" field blank, the variable always populates with "Default".  If I provide a default tag/branch in the field, that is the only tag/branch that will ever build.  

This seems like such a simple thing to do, I'm pretty much convinced I'm missing something.  I appreciate any help.  I welcome any solution that doesn't require more work than duplicating all my configurations.