diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -154,6 +154,8 @@
     'ArcanistDiffParserTestCase' => 'parser/__tests__/ArcanistDiffParserTestCase.php',
     'ArcanistDiffUtils' => 'difference/ArcanistDiffUtils.php',
     'ArcanistDiffUtilsTestCase' => 'difference/__tests__/ArcanistDiffUtilsTestCase.php',
+    'ArcanistDiffVectorNode' => 'difference/ArcanistDiffVectorNode.php',
+    'ArcanistDiffVectorTree' => 'difference/ArcanistDiffVectorTree.php',
     'ArcanistDiffWorkflow' => 'workflow/ArcanistDiffWorkflow.php',
     'ArcanistDifferentialCommitMessage' => 'differential/ArcanistDifferentialCommitMessage.php',
     'ArcanistDifferentialCommitMessageParserException' => 'differential/ArcanistDifferentialCommitMessageParserException.php',
@@ -691,7 +693,6 @@
     'PhutilExecutionEnvironment' => 'utils/PhutilExecutionEnvironment.php',
     'PhutilFileLock' => 'filesystem/PhutilFileLock.php',
     'PhutilFileLockTestCase' => 'filesystem/__tests__/PhutilFileLockTestCase.php',
-    'PhutilFileTree' => 'filesystem/PhutilFileTree.php',
     'PhutilFrenchLocale' => 'internationalization/locales/PhutilFrenchLocale.php',
     'PhutilGermanLocale' => 'internationalization/locales/PhutilGermanLocale.php',
     'PhutilGitBinaryAnalyzer' => 'filesystem/binary/PhutilGitBinaryAnalyzer.php',
@@ -1134,6 +1135,8 @@
     'ArcanistDiffParserTestCase' => 'PhutilTestCase',
     'ArcanistDiffUtils' => 'Phobject',
     'ArcanistDiffUtilsTestCase' => 'PhutilTestCase',
+    'ArcanistDiffVectorNode' => 'Phobject',
+    'ArcanistDiffVectorTree' => 'Phobject',
     'ArcanistDiffWorkflow' => 'ArcanistWorkflow',
     'ArcanistDifferentialCommitMessage' => 'Phobject',
     'ArcanistDifferentialCommitMessageParserException' => 'Exception',
@@ -1702,7 +1705,6 @@
     'PhutilExecutionEnvironment' => 'Phobject',
     'PhutilFileLock' => 'PhutilLock',
     'PhutilFileLockTestCase' => 'PhutilTestCase',
-    'PhutilFileTree' => 'Phobject',
     'PhutilFrenchLocale' => 'PhutilLocale',
     'PhutilGermanLocale' => 'PhutilLocale',
     'PhutilGitBinaryAnalyzer' => 'PhutilBinaryAnalyzer',
diff --git a/src/difference/ArcanistDiffVectorNode.php b/src/difference/ArcanistDiffVectorNode.php
new file mode 100644
--- /dev/null
+++ b/src/difference/ArcanistDiffVectorNode.php
@@ -0,0 +1,113 @@
+<?php
+
+final class ArcanistDiffVectorNode
+  extends Phobject {
+
+  private $vector;
+  private $children = array();
+  private $parentNode;
+  private $displayNode;
+  private $displayVector;
+  private $displayDepth;
+  private $valueNode;
+  private $attributes = array();
+
+  public function setVector(array $vector) {
+    $this->vector = $vector;
+    return $this;
+  }
+
+  public function getVector() {
+    return $this->vector;
+  }
+
+  public function getChildren() {
+    return $this->children;
+  }
+
+  public function setParentNode(ArcanistDiffVectorNode $parent) {
+    $this->parentNode = $parent;
+    return $this;
+  }
+
+  public function getParentNode() {
+    return $this->parentNode;
+  }
+
+  public function addChild(array $vector, $length, $idx) {
+    $is_node = ($idx === ($length - 1));
+    $element = $vector[$idx];
+
+    if (!isset($this->children[$element])) {
+      $this->children[$element] = id(new self())
+        ->setParentNode($this)
+        ->setVector(array_slice($vector, 0, $idx + 1));
+    }
+
+    $child = $this->children[$element];
+
+    if ($is_node) {
+      $child->setValueNode($child);
+      return;
+    }
+
+    $child->addChild($vector, $length, $idx + 1);
+  }
+
+  public function getDisplayVector() {
+    return $this->displayVector;
+  }
+
+  public function appendDisplayElement($element) {
+    if ($this->displayVector === null) {
+      $this->displayVector = array();
+    }
+
+    $this->displayVector[] = $element;
+
+    return $this;
+  }
+
+  public function setDisplayNode(ArcanistDiffVectorNode $display_node) {
+    $this->displayNode = $display_node;
+    return $this;
+  }
+
+  public function getDisplayNode() {
+    return $this->displayNode;
+  }
+
+  public function setDisplayDepth($display_depth) {
+    $this->displayDepth = $display_depth;
+    return $this;
+  }
+
+  public function getDisplayDepth() {
+    return $this->displayDepth;
+  }
+
+  public function setValueNode($value_node) {
+    $this->valueNode = $value_node;
+    return $this;
+  }
+
+  public function getValueNode() {
+    return $this->valueNode;
+  }
+
+  public function setAncestralAttribute($key, $value) {
+    $this->attributes[$key] = $value;
+
+    $parent = $this->getParentNode();
+    if ($parent) {
+      $parent->setAncestralAttribute($key, $value);
+    }
+
+    return $this;
+  }
+
+  public function getAttribute($key, $default = null) {
+    return idx($this->attributes, $key, $default);
+  }
+
+}
diff --git a/src/difference/ArcanistDiffVectorTree.php b/src/difference/ArcanistDiffVectorTree.php
new file mode 100644
--- /dev/null
+++ b/src/difference/ArcanistDiffVectorTree.php
@@ -0,0 +1,95 @@
+<?php
+
+final class ArcanistDiffVectorTree
+  extends Phobject {
+
+  private $vectors;
+
+  public function addVector(array $vector) {
+    $this->vectors[] = $vector;
+    return $this;
+  }
+
+  public function newDisplayList() {
+    $root = new ArcanistDiffVectorNode();
+
+    foreach ($this->vectors as $vector) {
+      $root->addChild($vector, count($vector), 0);
+    }
+
+    foreach ($root->getChildren() as $child) {
+      $this->compressTree($child);
+    }
+
+    $root->setDisplayDepth(-1);
+    foreach ($root->getChildren() as $child) {
+      $this->updateDisplayDepth($child);
+    }
+
+    return $this->getDisplayList($root);
+  }
+
+  private function compressTree(ArcanistDiffVectorNode $node) {
+    $display_node = $node;
+
+    $children = $node->getChildren();
+    if ($children) {
+      $parent = $node->getParentNode();
+      if ($parent) {
+        $siblings = $parent->getChildren();
+        if (count($siblings) === 1) {
+          if (!$parent->getValueNode()) {
+            $parent_display = $parent->getDisplayNode();
+            if ($parent_display) {
+              $display_node = $parent_display;
+              if ($node->getValueNode()) {
+                $parent->setValueNode($node->getValueNode());
+              }
+            }
+          }
+        }
+      }
+    }
+
+    $node->setDisplayNode($display_node);
+
+    $display_element = last($node->getVector());
+    $display_node->appendDisplayElement($display_element);
+
+    foreach ($children as $child) {
+      $this->compressTree($child);
+    }
+  }
+
+  private function updateDisplayDepth(ArcanistDiffVectorNode $node) {
+    $parent_depth = $node->getParentNode()->getDisplayDepth();
+
+    if ($node->getDisplayVector() === null) {
+      $display_depth = $parent_depth;
+    } else {
+      $display_depth = $parent_depth + 1;
+    }
+
+    $node->setDisplayDepth($display_depth);
+
+    foreach ($node->getChildren() as $child) {
+      $this->updateDisplayDepth($child);
+    }
+  }
+
+  private function getDisplayList(ArcanistDiffVectorNode $node) {
+    $result = array();
+
+    foreach ($node->getChildren() as $child) {
+      if ($child->getDisplayVector() !== null) {
+        $result[] = $child;
+      }
+      foreach ($this->getDisplayList($child) as $item) {
+        $result[] = $item;
+      }
+    }
+
+    return $result;
+  }
+
+}
diff --git a/src/filesystem/PhutilFileTree.php b/src/filesystem/PhutilFileTree.php
deleted file mode 100644
--- a/src/filesystem/PhutilFileTree.php
+++ /dev/null
@@ -1,112 +0,0 @@
-<?php
-
-/**
- * Data structure for representing filesystem directory trees.
- */
-final class PhutilFileTree extends Phobject {
-
-  private $name;
-  private $fullPath;
-  private $data;
-  private $depth = 0;
-  private $parentNode;
-  private $children = array();
-
-  public function addPath($path, $data) {
-    $parts = $this->splitPath($path);
-    $parts = array_reverse($parts);
-    $this->insertPath($parts, $data);
-    return $this;
-  }
-
-  public function destroy() {
-    $this->parentNode = null;
-    foreach ($this->children as $child) {
-      $child->destroy();
-    }
-    $this->children = array();
-    return $this;
-  }
-
-  /**
-   * Get the next node, iterating in depth-first order.
-   */
-  public function getNextNode() {
-    if ($this->children) {
-      return head($this->children);
-    }
-    $cursor = $this;
-    while ($cursor) {
-      if ($cursor->getNextSibling()) {
-        return $cursor->getNextSibling();
-      }
-      $cursor = $cursor->parentNode;
-    }
-    return null;
-  }
-
-  public function getName() {
-    return $this->name;
-  }
-
-  public function getFullPath() {
-    return $this->fullPath;
-  }
-
-  public function getDepth() {
-    return $this->depth;
-  }
-
-  public function getData() {
-    return $this->data;
-  }
-
-  protected function insertPath(array $parts, $data) {
-    $part = array_pop($parts);
-    if ($part === null) {
-      if ($this->data) {
-        $full_path = $this->getFullPath();
-        throw new Exception(
-          pht("Duplicate insertion for path '%s'.", $full_path));
-      }
-      $this->data = $data;
-      return;
-    }
-
-    if (empty($this->children[$part])) {
-      $node = new PhutilFileTree();
-      $node->parentNode = $this;
-      $node->depth = $this->depth + 1;
-      $node->name = $part;
-      $node->fullPath = $this->parentNode ? ($this->fullPath.'/'.$part) : $part;
-      $this->children[$part] = $node;
-    }
-
-    $this->children[$part]->insertPath($parts, $data);
-  }
-
-  protected function splitPath($path) {
-    $path = trim($path, '/');
-    $parts = preg_split('@/+@', $path);
-    return $parts;
-  }
-
-  protected function getNextSibling() {
-    if (!$this->parentNode) {
-      return null;
-    }
-
-    $found = false;
-    foreach ($this->parentNode->children as $node) {
-      if ($found) {
-        return $node;
-      }
-      if ($this->name === $node->name) {
-        $found = true;
-      }
-    }
-
-    return null;
-  }
-
-}