howto handle name clashes

Hi,

how to handle name clashes for branches and tags? Is there anything I can add to the refspec to make the name unique?

E.g.
- for merging "git merge --no-ff refs/branches/test" works, but
generates a not so nice default merge message. ("merged  commit
refs/branches/test" instead of "merged branch test")
- how to drop a remote tag/branch ("git push origin :test" does not work)