code: def check_if_remote_head_is_different() -> Union[bool, None]:
      """Checks if remote git repository is different than the version available locally.
  
      This only compares the local SHA to the HEAD commit of a given branch. This check won't be used if user isn't in a
      HEAD locally.
  
      """
      # Check SHA values.
      local_sha = execute_git_command(["rev-parse", "@"])
      remote_sha = execute_git_command(["rev-parse", r"@{u}"])
      base_sha = execute_git_command(["merge-base", "@", r"@{u}"])
  
      # Whenever a SHA is not avaialble, just return.
      if any("fatal" in f for f in (local_sha, remote_sha, base_sha)):
          return None
  
      return local_sha not in (remote_sha, base_sha)
  
file_path: pytorch-lightning/src/lightning/app/utilities/git.py
imports: import subprocess
  from pathlib import Path
  from typing import List, Union
label_desc: Use image node_id 5 for calling a global function with example usage: check_if_remote_head_is_different() and returns: unknown, None