Function merge_notes 

pub fn merge_notes(
    git_dir: &Path,
    format: ObjectFormat,
    store: &FileRefStore,
    local_ref: &NotesRef,
    remote_ref: &NotesRef,
    strategy: NotesMergeStrategy,
    message: &str,
    identity: &NotesCommitIdentity,
) -> Result<NotesMergeOutcome>

Merge remote_ref into local_ref, matching Git’s note-level three-way merge rules. The caller is responsible for persisting conflict worktree files when NotesMergeOutcome::Conflicted is returned.