rebase -i --update-refs can lead to deletion of branches

Hi,

I have the following:

While doing a

`$ git rebase --interactive  --update-refs X`

I *removed* the "update-ref" lines from the todo list. The rebase runs as expected and prints e.g.

``` Successfully rebased and updated refs/heads/test. Updated the following refs with --update-refs: refs/heads/master refs/heads/permissive-interactive-rebase refs/heads/variable-annotations-meta-block ```

After that all refs have been removed/deleted.

```
$ git branch  --list
* test
```

Now, I should just have not used `--update-refs` in the first place but anyway I decide late that I rather don't want to update "master" etc. and it should probably not delete the local refs.

Actually, I so love the new feature that I switched it *on* by default, and just wanted to overwrite the behavior in the todo editor.

Regards Caspar Duregger