Function resolve_function_rename 

pub fn resolve_function_rename(
    path: &Path,
    old_content: &str,
    new_content: &str,
    old_name: &str,
    similarity_method: SimilarityMethod,
) -> FunctionRenameResolution

Resolve the new name of one function within a single file.

Candidates come from parsed function definitions that are new under their qualified identity and share the original definition’s container. This deliberately excludes text search and existing, unchanged neighbours.