When I run `arc patch` I sometimes get an error with a question, to which I usually answer 'no'. Example:
```
$ arc patch D98155
Created and checked out branch arcpatch-D98155.
This diff is against commit ebe436220476a97f83a9e92d6a5f18f56078dfb5, but
the commit is nowhere in the working copy. Try to apply it against the
current working copy state? (0a6d5dbdd88cdda8acf77004a6fd266396e16c8d)
[Y/n] n
Usage Exception: User aborted the workflow.
```
In such cases arc leaves behind a useless branch. Shouldn't it remove that branch (given that it always creates a new branch anyway) or perhaps check for such error conditions earlier in its flow?