parameters: (git_dir: str, ref_a: str, ref_b: str)
return_statement: return subprocess.check_output(
        ['git', '-C', git_dir, 'merge-base', ref_a, ref_b],
        encoding='utf-8',
    ).strip()
docstring: Finds the closest common parent commit between `ref_a` and `ref_b`.
docstring_summary: Finds the closest common parent commit between `ref_a` and `ref_b`.
docstring_tokens: Finds the closest common parent commit between ref_a and ref_b .
function: def _find_common_parent_commit(git_dir: str, ref_a: str, ref_b: str) -> str:
    """Finds the closest common parent commit between `ref_a` and `ref_b`."""
    return subprocess.check_output(
        ['git', '-C', git_dir, 'merge-base', ref_a, ref_b],
        encoding='utf-8',
    ).strip()
function_tokens: def _find_common_parent_commit ( git_dir : str , ref_a : str , ref_b : str ) -> str : return subprocess . check_output ( [ 'git' , '-C' , git_dir , 'merge-base' , ref_a , ref_b ] , encoding = 'utf-8' , ) . strip ( )