code: def fix_exp_head(
      scm: Union["Git", "NoSCM"], ref: Optional[str]
  ) -> Optional[str]:
      if ref:
          name, tail = Git.split_ref_pattern(ref)
          if name == "HEAD" and scm.get_ref(EXEC_BASELINE):
              return f"{EXEC_BASELINE}{tail}"
      return ref
  
imports: import os
  import random
  import sys
  from collections import defaultdict
  from functools import wraps
  from typing import TYPE_CHECKING, Callable, Dict, Generator, Iterable, List, Mapping, Optional, Set, Tuple, Union
  from dvc.exceptions import InvalidArgumentError
  from dvc.repo.experiments.exceptions import AmbiguousExpRefInfo
  from dvc.rwlock import rwlock
  from dvc.scm import Git
  from .refs import EXEC_APPLY, EXEC_BASELINE, EXEC_BRANCH, EXPS_NAMESPACE, ITER_SKIP_NAMESPACES, STASHES, ExpRefInfo
label_desc: Use image node_id 14 for calling a global function with example usage: fix_exp_head(scm, ref) and returns: ref, EXEC_BASELINE, tail