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.
Using "stale" as a name for a branch that is some number of commits behind main. 
I make it be behind main by branching before adding commits to main.
Any ideas for better wording / setup for the test?