git prune-branches

@kevgo please review

+ Changed a couple git helpers to take in parameters instead of operating on the current branch
+ Set the default branch on the remote repo to main (needed as the git prune-branches feature specs were deleting the master branch (since its not main) and you cannot delete the HEAD branch on the remote repo.
How do you feel about combining the first two steps?

```cucumber
Given I am on a feature branch "old_feature" behind main
```