Git tag for a subfolder of a repository

I use Git to import a SVN repository. Then I created my own project as a subfolder in the repository.

I use the SVN repository with Git-SVN. My working procedure is:

1. git commit -am "message"
2. git svn rebase
3. git svn dcommit.

Now I want to tag my project with git tag -a RC1 -m 'Release Candidate 1', but I only want that my project gets the tag.

How can I do that?