code: def get_current_branch(self, location):
          
          # git-symbolic-ref exits with empty stdout if "HEAD" is a detached
          # HEAD rather than a symbolic ref.  In addition, the -q causes the
          # command to exit with status code 1 instead of 128 in this case
          # and to suppress the message to stderr.
          args = ['symbolic-ref', '-q', 'HEAD']
          output = self.run_command(
              args, extra_ok_returncodes=(1, ), show_stdout=False, cwd=location,
          )
          ref = output.strip()
  
          if ref.startswith('refs/heads/'):
              return ref[len('refs/heads/'):]
  
          return None
docs: Return the current branch, or None if HEAD isn't at a branch
          (e.g. detached HEAD).