Using pull new in a headless checkout results in a push of the HEAD hash as a remote branch name

If you commit something without being on a branch and then do a new pull request, git-hub tries something that doesn't look very smart (not that it was smart to begin with to do a pull request without being on a branch):

```
➜  <project> git:(d1aada8) ✗ git hub pull new          
Pushing d1aada84d040b61e42335ea0fb62d73248a73dd1 to d1aada84d040b61e42335ea0fb62d73248a73dd1 in origin
```