change remote to track new branch

Hi:

Long ago I added a remote to my repo. It is set to track what was then WordPress' main release branch (3.4-branch) and created a local branch to use it. Well, time marches on. I want to update my remote and branch to track the new main release branch (3.6-branch).

Here's how I set things up at the time:

git remote add -t 3.4-branch -f wp https://github.com/WordPress/WordPress git checkout -b wp wp/3.4-branch

I've tried various fetch, remote and branch commands to effectuate this change, to no avail. I get messages like "Not a valid ref."

I know a major part of this is that my repo only knows of one remote branch (of the many that exist). What I don't know are the commands needed to fetch the right remote branch, set my remote and local branch to track it. Your help will be appreciated, please.

Here's some information on the current state of things:

vvvvvvvvvvvvvvvvvvvv
^^^^^^^^^^^^^^^^^^^^
git branch -av
  dev                                 a18677e [ahead 153] backup of 3.4 db
  master                              0d6f9b5 Merge branch 'dev'

* wp                                  42abc67 [ahead 5] Merge branch
'3.4-branch' of https://github.com/WordPress/WordPress into wp

  remotes/git_push_deployer/wordpress c8a5d69 Make my branch names generic.
  remotes/prod/HEAD                   -> prod/master
  remotes/prod/master                 0d6f9b5 Merge branch 'dev'
  remotes/wp/3.4-branch               b535358 POT, generated from r24100
  remotes/wpconfig/master             3e45a81 LSS 0.27.0.
^^^^^^^^^^^^^^^^^^^^

vvvvvvvvvvvvvvvvvvvv
git remote show wp
* remote wp
  Fetch URL: https://github.com/WordPress/WordPress
  Push  URL: https://github.com/WordPress/WordPress
  HEAD branch: master
  Remote branch:
    3.4-branch tracked
  Local branch configured for 'git pull':
    wp merges with remote 3.4-branch
  Local ref configured for 'git push':
    master pushes to master (local out of date)
^^^^^^^^^^^^^^^^^^^^

Thanks,

--Dan