title: refname is ambiguous and pull failing
body: <p>I ran the following command as I wanted to move my production branch back without having to checkout first:</p>
  
  <pre><code>git branch -f production HEAD~1
  </code></pre>
  
  <p>I am now getting the following warning when I checkout production:</p>
  
  <pre><code>warning: refname 'production' is ambiguous.
  </code></pre>
  
  <p>I then run:</p>
  
  <pre><code>git pull
  </code></pre>
  
  <p>And I receive the following error:</p>
  
  <pre><code>First, rewinding head to replay your work on top of it...
  Fast-forwarded production to 7463e01c536ad52746b8879ef3d70ffd5a8db31e.
  error: Ref refs/heads/production is at 252038dfa22caba8a816a68dcb005c625e44c51f but expected ae5b621609c1b5b430e3d30711157298f842942a
  fatal: Cannot lock the ref 'refs/heads/production'
  Could not move back to refs/heads/production
  </code></pre>
  
  <p>I can pull on other branches though. How can I fix this?</p>
  
  <p><strong>Further Info</strong></p>
  
  <p><code>git tag</code> doesn't return any output. I previously had a production repository, but I've now renamed it to live</p>
  
  <pre><code>&gt; ~/repo (chris-membership-fees)$ git show-ref | grep production
  88e0c37c9ae4ff6967ddd027b62b62fa2c0ac272 refs/heads/production
  9d739cff44a898f0c68da33fb22a230985e479ce refs/remotes/backup/production
  
  ~/repo (chris-membership-fees)$ git branch -a | grep production
    production
    remotes/backup/production
  </code></pre>
  
  <p><strong>Log</strong></p>
  
  <p>I tagged the first revision as a and the second as b (note that the revision numbers have changed as production is now different). This is the log, simplified by decoration</p>
  
  <pre><code>* commit 7463e01c536ad52746b8879ef3d70ffd5a8db31e (**tag: a**, backup/live-master, production, live-master)
  | 
  | Date:   Wed Dec 28 11:47:49 2011 +1100
  | 
  |     Merge remote-tracking branch 'origin/joseph-quick-fix'
  |  
  * commit f35f0259c4e36d46dd1df71b3293bef6105cef98 (origin/hotfix-googleplusdirectconnect)
  | 
  | Date:   Fri Dec 23 12:25:27 2011 +1100
  | 
  |     Add google plus link tag to home page for direct connect
  |    
  *   commit 8b3a30ef2909439ac18b65ebbb316eb0cdd2d61c
  |\  Merge: f696f3e 88e0c37
  | | 
  | | Date:   Wed Dec 21 14:28:45 2011 +1100
  | | 
  | |     Merge branch 'master' into chris-hotfix
  | |   
  * | commit f696f3e2b8f4a19ec2b2c2a3638c68e7a52836e3 (origin/chris-hotfix, backup/chris-hotfix, chris-hotfix)
  | | 
  | | Date:   Wed Dec 21 11:56:10 2011 +1100
  | | 
  | |     Fixed buyer price info
  | |     
  | *   commit 88e0c37c9ae4ff6967ddd027b62b62fa2c0ac272
  | |\  Merge: c9655da ae5b621
  | |/  
  |/|   Date:   Wed Dec 21 11:53:36 2011 +1100
  | |   
  | |       Merge branch 'master' of git.freelancer.com:production into production
  | |   
  * | commit ae5b621609c1b5b430e3d30711157298f842942a (HEAD, **tag: b**)
  | | 
  | | Date:   Wed Dec 21 10:51:47 2011 +1100
  | | 
  | |     Merge branch 'master' of git.freelancer.com:production
  | |   
  | * commit c9655da9c1627ab53720ae818affdd1e6f14119f (origin/game-shadow2)
  | | 
  | | Date:   Tue Dec 20 18:41:57 2011 -0500
  | | 
  | |     * Removed debugging code
  | |     
  | *   commit ca88d33538bd3b99ea7c186b5b531e611847989d
  | |\  Merge: 99e983a c397a8b
  | |/  
  |/|   Date:   Tue Dec 20 17:25:24 2011 -0500
  | |   
  | |       Merge remote-tracking branch 'production/master' into shadow2
  </code></pre>