I have a number of modules in CVS with different tags. How would I go about getting the name of the branch these tagged files exist on? I've tried checking out a file from the module using cvs co -r TAG and then doing cvs log but it appears to give me a list of all of the branches that the file exists on, rather than just a single branch name.

Also this needs to be an automated process, so I can't use web based tools like viewvc to gather this info.