Function combined_diff_paths_trees 

pub fn combined_diff_paths_trees(
    odb: &Odb,
    merge_tree: &ObjectId,
    parent_trees: &[Option<ObjectId>],
    walk: &CombinedTreeDiffOptions,
    find_object: Option<&ObjectId>,
) -> Result<Vec<CombinedDiffPath>>

Combined diff paths when parents are already tree OIDs (plumbing git diff --cc with N+1 trees).