How to convert SVN tags to git tags?

["Steve Keller" <keller.steve@xxxxxx>]

After converting from SVN to git using git svn init + git svn fetch,
my SVN tags appear as remote branches in git.  I find many suggestions
to convert these to git tags by calling git tag -a <tag-name> <branch-name>
but this gives something like this

               C4
               |
               V
    T -> C3 -> C2
               |
               V
               C1

that is, I still have a branch with only 1 commit C3 and I have a tag T
pointing to that commit.  Also, T will have a current timestamp.  I'd
prefer to get

               C4
               |
               V
          T -> C2
               |
               V
               C1

where T takes the commit message and date from C3.  How can I achieve
that?

Steve