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.
The branch "old_feature" never existed in my repo here. And it shouldn't prune other people's feature branches. What if I just start working on a branch, and you run "git prune-branches" and kill my branch?