gh pull-request always tells me I have unpushed commits

This code in pull_request.go is wrong:

```
 commits, _ := git.RefList(base, head)
 if !force && trackedBranch != nil && len(commits) > 0 {
                err = fmt.Errorf("Aborted: %d commits are not yet pushed to %s", len(commits), trackedBranch.LongName())
                err = fmt.Errorf("%s\n(use `-f` to force submit a pull request anyway)", err)
                utils.Check(err)
        }

```

My work flow is:
```
gh fork
git checkout -b my-fixes-branch
git commit -am "fixes"
git push dgryski -u my-fixes-branch
gh pull-request
```

It generates this error:
```
2013/12/18 21:27:53 fatal: Aborted: 1 commits are not yet pushed to dgryski/otp-case-fixes
(use `-f` to force submit a pull request anyway)
```

So isn't it complaining about exactly the one commit I want to push?  If I try to push to my branch, git tells me I'm up-to-date.  fullBase in this case is pointing at origin/master, but I think it should be the my tracked branch.