[little BUG] pushing to existing branch with remote-helper shows [new branch]

Hi,

Nothing serious, but I think this is a little bug in transport-helper. I noticed it working on git-remote-mediawiki, and could reproduce it with testgit:

/tmp/clone$ git push
To testgit::/tmp/repo
 * [new branch]      master -> master
/tmp/clone$ date >> foo.txt; git commit -am bar
[master 4438ced] bar
 1 files changed, 1 insertions(+), 0 deletions(-)
/tmp/clone$ git push
To testgit::/tmp/repo
 * [new branch]      master -> master

(/tmp/clone is a clone of testgit::/tmp/repo)