code: def git_clean(ctx):
      
      # Get command parts
      cmd_part_s = [
          # Program path
          'git',
  
          # Clean untracked files
          'clean',
  
          # Remove all untracked files
          '-x',
  
          # Remove untracked directories too
          '-d',
  
          # Force to remove
          '-f',
  
          # Give two `-f` flags to remove sub-repositories too
          '-f',
      ]
  
      # Print title
      print_title('git_clean')
  
      # Print the command in multi-line format
      print_text(_format_multi_line_command(cmd_part_s))
  
      # Create subprocess to run the command in top directory
      proc = subprocess.Popen(cmd_part_s, cwd=ctx.top_dir)
  
      # Wait the subprocess to finish
      proc.wait()
  
      # Print end title
      print_title('git_clean', is_end=True)
docs: Delete all files untracked by git.
  
      :param ctx: Context object.
  
      :return: None.