Index: node_modules/d3-hierarchy/src/tree.js
===================================================================
--- node_modules/d3-hierarchy/src/tree.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-hierarchy/src/tree.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,237 @@
+import {Node} from "./hierarchy/index.js";
+
+function defaultSeparation(a, b) {
+  return a.parent === b.parent ? 1 : 2;
+}
+
+// function radialSeparation(a, b) {
+//   return (a.parent === b.parent ? 1 : 2) / a.depth;
+// }
+
+// This function is used to traverse the left contour of a subtree (or
+// subforest). It returns the successor of v on this contour. This successor is
+// either given by the leftmost child of v or by the thread of v. The function
+// returns null if and only if v is on the highest level of its subtree.
+function nextLeft(v) {
+  var children = v.children;
+  return children ? children[0] : v.t;
+}
+
+// This function works analogously to nextLeft.
+function nextRight(v) {
+  var children = v.children;
+  return children ? children[children.length - 1] : v.t;
+}
+
+// Shifts the current subtree rooted at w+. This is done by increasing
+// prelim(w+) and mod(w+) by shift.
+function moveSubtree(wm, wp, shift) {
+  var change = shift / (wp.i - wm.i);
+  wp.c -= change;
+  wp.s += shift;
+  wm.c += change;
+  wp.z += shift;
+  wp.m += shift;
+}
+
+// All other shifts, applied to the smaller subtrees between w- and w+, are
+// performed by this function. To prepare the shifts, we have to adjust
+// change(w+), shift(w+), and change(w-).
+function executeShifts(v) {
+  var shift = 0,
+      change = 0,
+      children = v.children,
+      i = children.length,
+      w;
+  while (--i >= 0) {
+    w = children[i];
+    w.z += shift;
+    w.m += shift;
+    shift += w.s + (change += w.c);
+  }
+}
+
+// If vi-’s ancestor is a sibling of v, returns vi-’s ancestor. Otherwise,
+// returns the specified (default) ancestor.
+function nextAncestor(vim, v, ancestor) {
+  return vim.a.parent === v.parent ? vim.a : ancestor;
+}
+
+function TreeNode(node, i) {
+  this._ = node;
+  this.parent = null;
+  this.children = null;
+  this.A = null; // default ancestor
+  this.a = this; // ancestor
+  this.z = 0; // prelim
+  this.m = 0; // mod
+  this.c = 0; // change
+  this.s = 0; // shift
+  this.t = null; // thread
+  this.i = i; // number
+}
+
+TreeNode.prototype = Object.create(Node.prototype);
+
+function treeRoot(root) {
+  var tree = new TreeNode(root, 0),
+      node,
+      nodes = [tree],
+      child,
+      children,
+      i,
+      n;
+
+  while (node = nodes.pop()) {
+    if (children = node._.children) {
+      node.children = new Array(n = children.length);
+      for (i = n - 1; i >= 0; --i) {
+        nodes.push(child = node.children[i] = new TreeNode(children[i], i));
+        child.parent = node;
+      }
+    }
+  }
+
+  (tree.parent = new TreeNode(null, 0)).children = [tree];
+  return tree;
+}
+
+// Node-link tree diagram using the Reingold-Tilford "tidy" algorithm
+export default function() {
+  var separation = defaultSeparation,
+      dx = 1,
+      dy = 1,
+      nodeSize = null;
+
+  function tree(root) {
+    var t = treeRoot(root);
+
+    // Compute the layout using Buchheim et al.’s algorithm.
+    t.eachAfter(firstWalk), t.parent.m = -t.z;
+    t.eachBefore(secondWalk);
+
+    // If a fixed node size is specified, scale x and y.
+    if (nodeSize) root.eachBefore(sizeNode);
+
+    // If a fixed tree size is specified, scale x and y based on the extent.
+    // Compute the left-most, right-most, and depth-most nodes for extents.
+    else {
+      var left = root,
+          right = root,
+          bottom = root;
+      root.eachBefore(function(node) {
+        if (node.x < left.x) left = node;
+        if (node.x > right.x) right = node;
+        if (node.depth > bottom.depth) bottom = node;
+      });
+      var s = left === right ? 1 : separation(left, right) / 2,
+          tx = s - left.x,
+          kx = dx / (right.x + s + tx),
+          ky = dy / (bottom.depth || 1);
+      root.eachBefore(function(node) {
+        node.x = (node.x + tx) * kx;
+        node.y = node.depth * ky;
+      });
+    }
+
+    return root;
+  }
+
+  // Computes a preliminary x-coordinate for v. Before that, FIRST WALK is
+  // applied recursively to the children of v, as well as the function
+  // APPORTION. After spacing out the children by calling EXECUTE SHIFTS, the
+  // node v is placed to the midpoint of its outermost children.
+  function firstWalk(v) {
+    var children = v.children,
+        siblings = v.parent.children,
+        w = v.i ? siblings[v.i - 1] : null;
+    if (children) {
+      executeShifts(v);
+      var midpoint = (children[0].z + children[children.length - 1].z) / 2;
+      if (w) {
+        v.z = w.z + separation(v._, w._);
+        v.m = v.z - midpoint;
+      } else {
+        v.z = midpoint;
+      }
+    } else if (w) {
+      v.z = w.z + separation(v._, w._);
+    }
+    v.parent.A = apportion(v, w, v.parent.A || siblings[0]);
+  }
+
+  // Computes all real x-coordinates by summing up the modifiers recursively.
+  function secondWalk(v) {
+    v._.x = v.z + v.parent.m;
+    v.m += v.parent.m;
+  }
+
+  // The core of the algorithm. Here, a new subtree is combined with the
+  // previous subtrees. Threads are used to traverse the inside and outside
+  // contours of the left and right subtree up to the highest common level. The
+  // vertices used for the traversals are vi+, vi-, vo-, and vo+, where the
+  // superscript o means outside and i means inside, the subscript - means left
+  // subtree and + means right subtree. For summing up the modifiers along the
+  // contour, we use respective variables si+, si-, so-, and so+. Whenever two
+  // nodes of the inside contours conflict, we compute the left one of the
+  // greatest uncommon ancestors using the function ANCESTOR and call MOVE
+  // SUBTREE to shift the subtree and prepare the shifts of smaller subtrees.
+  // Finally, we add a new thread (if necessary).
+  function apportion(v, w, ancestor) {
+    if (w) {
+      var vip = v,
+          vop = v,
+          vim = w,
+          vom = vip.parent.children[0],
+          sip = vip.m,
+          sop = vop.m,
+          sim = vim.m,
+          som = vom.m,
+          shift;
+      while (vim = nextRight(vim), vip = nextLeft(vip), vim && vip) {
+        vom = nextLeft(vom);
+        vop = nextRight(vop);
+        vop.a = v;
+        shift = vim.z + sim - vip.z - sip + separation(vim._, vip._);
+        if (shift > 0) {
+          moveSubtree(nextAncestor(vim, v, ancestor), v, shift);
+          sip += shift;
+          sop += shift;
+        }
+        sim += vim.m;
+        sip += vip.m;
+        som += vom.m;
+        sop += vop.m;
+      }
+      if (vim && !nextRight(vop)) {
+        vop.t = vim;
+        vop.m += sim - sop;
+      }
+      if (vip && !nextLeft(vom)) {
+        vom.t = vip;
+        vom.m += sip - som;
+        ancestor = v;
+      }
+    }
+    return ancestor;
+  }
+
+  function sizeNode(node) {
+    node.x *= dx;
+    node.y = node.depth * dy;
+  }
+
+  tree.separation = function(x) {
+    return arguments.length ? (separation = x, tree) : separation;
+  };
+
+  tree.size = function(x) {
+    return arguments.length ? (nodeSize = false, dx = +x[0], dy = +x[1], tree) : (nodeSize ? null : [dx, dy]);
+  };
+
+  tree.nodeSize = function(x) {
+    return arguments.length ? (nodeSize = true, dx = +x[0], dy = +x[1], tree) : (nodeSize ? [dx, dy] : null);
+  };
+
+  return tree;
+}