Better -branches:.

`-allBranchesWithError:` doesn't really work in the face of multiple remotes since it doesn't actually look up tracking branches and instead simply de-dupes based on name. This new method does The Right Thing®.

I went with a new method over fixing `-allBranches...` because it seemed bad to silently change the semantics of the method. But maybe we don't really care? :trolleybus: 
Nah, that's still success.

I didn't feel terribly strong about how we should handle this error, and thinking about it now it's probably more helpful to at least add the local branch in this case. Skipping the branch entirely seems wrong.