Function tree_diff_dirs 

pub fn tree_diff_dirs<G>(
    graph: &G,
    old_tree: Option<NodeId>,
    new_tree: NodeId,
    limit: Option<usize>,
) -> Result<TreeDiff>
where
    G: SwhLabeledForwardGraph + SwhGraphWithProperties<Maps: Maps>,

Compute a tree diff between the old and new trees rooted in the nodes supplied, which are required to be directory nodes.

The limit parameter can optionally limit the number of diff elements to return (to avoid returning very big diffs from git bombs). If this limit is reached, an error is returned.

If no old_tree is supplied, then all the files present in new_tree are treated as being added.

WARNING: rename detection is currently not supported. The Moved variant is never returned.