code: def guess_folder_vcs(folder):
      
      try:
          contents = os.listdir(folder)
          vcs_folders = ['.git', '.hg', '.svn']
          found = next((x for x in vcs_folders if x in contents), None)
          # Chop off the dot if we got a string back
          return found[1:] if found else None
      except OSError:
          return None
docs: Given a path for a folder on the local filesystem, see what kind of vcs
      repo it is, if any.