diff --git a/src/applications/phriction/markup/PhrictionRemarkupRule.php b/src/applications/phriction/markup/PhrictionRemarkupRule.php
index c3a795a524..9c5649bbbe 100644
--- a/src/applications/phriction/markup/PhrictionRemarkupRule.php
+++ b/src/applications/phriction/markup/PhrictionRemarkupRule.php
@@ -1,188 +1,198 @@
 <?php
 
 final class PhrictionRemarkupRule extends PhutilRemarkupRule {
 
   const KEY_RULE_PHRICTION_LINK = 'phriction.link';
 
   public function getPriority() {
     return 175.0;
   }
 
   public function apply($text) {
     return preg_replace_callback(
       '@\B\\[\\[([^|\\]]+)(?:\\|([^\\]]+))?\\]\\]\B@U',
       array($this, 'markupDocumentLink'),
       $text);
   }
 
   public function markupDocumentLink(array $matches) {
-    $link = trim($matches[1]);
+    // If the link contains an anchor, separate that off first.
+    $parts = explode('#', trim($matches[1]), 2);
+    if (count($parts) == 2) {
+      $link = $parts[0];
+      $anchor = $parts[1];
+    } else {
+      $link = $parts[0];
+      $anchor = null;
+    }
 
     // Handle relative links.
     if ((substr($link, 0, 2) === './') || (substr($link, 0, 3) === '../')) {
       $base = null;
       $context = $this->getEngine()->getConfig('contextObject');
       if ($context !== null && $context instanceof PhrictionContent) {
         // Handle content when it's being rendered in document view.
         $base = $context->getSlug();
       }
       if ($context !== null && is_array($context) &&
           idx($context, 'phriction.isPreview')) {
         // Handle content when it's a preview for the Phriction editor.
         $base = idx($context, 'phriction.slug');
       }
       if ($base !== null) {
         $base_parts = explode('/', rtrim($base, '/'));
         $rel_parts = explode('/', rtrim($link, '/'));
         foreach ($rel_parts as $part) {
           if ($part === '.') {
             // Consume standalone dots in a relative path, and do
             // nothing with them.
           } else if ($part === '..') {
             if (count($base_parts) > 0) {
               array_pop($base_parts);
             }
           } else {
             array_push($base_parts, $part);
           }
         }
         $link = implode('/', $base_parts).'/';
       }
     }
 
     $name = trim(idx($matches, 2, ''));
     if (empty($matches[2])) {
       $name = null;
     }
 
     // Link is now used for slug detection, so append a slash if one
     // is needed.
     $link = rtrim($link, '/').'/';
 
     $engine = $this->getEngine();
     $token = $engine->storeText('x');
     $metadata = $engine->getTextMetadata(
       self::KEY_RULE_PHRICTION_LINK,
       array());
     $metadata[] = array(
       'token' => $token,
       'link' => $link,
+      'anchor' => $anchor,
       'explicitName' => $name,
     );
     $engine->setTextMetadata(self::KEY_RULE_PHRICTION_LINK, $metadata);
 
     return $token;
   }
 
   public function didMarkupText() {
     $engine = $this->getEngine();
     $metadata = $engine->getTextMetadata(
       self::KEY_RULE_PHRICTION_LINK,
       array());
 
     if (!$metadata) {
       return;
     }
 
     $slugs = ipull($metadata, 'link');
     foreach ($slugs as $key => $slug) {
       $slugs[$key] = PhabricatorSlug::normalize($slug);
     }
 
     // We have to make two queries here to distinguish between
     // documents the user can't see, and documents that don't
     // exist.
     $visible_documents = id(new PhrictionDocumentQuery())
       ->setViewer($engine->getConfig('viewer'))
       ->withSlugs($slugs)
       ->needContent(true)
       ->execute();
     $existant_documents = id(new PhrictionDocumentQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withSlugs($slugs)
       ->execute();
 
     $visible_documents = mpull($visible_documents, null, 'getSlug');
     $existant_documents = mpull($existant_documents, null, 'getSlug');
 
     foreach ($metadata as $spec) {
       $link = $spec['link'];
       $slug = PhabricatorSlug::normalize($link);
       $name = $spec['explicitName'];
       $class = 'phriction-link';
 
       // If the name is something meaningful to humans, we'll render this
       // in text as: "Title" <link>. Otherwise, we'll just render: <link>.
       $is_interesting_name = (bool)strlen($name);
 
       if (idx($existant_documents, $slug) === null) {
         // The target document doesn't exist.
         if ($name === null) {
           $name = explode('/', trim($link, '/'));
           $name = end($name);
         }
         $class = 'phriction-link-missing';
       } else if (idx($visible_documents, $slug) === null) {
         // The document exists, but the user can't see it.
         if ($name === null) {
           $name = explode('/', trim($link, '/'));
           $name = end($name);
         }
         $class = 'phriction-link-lock';
       } else {
         if ($name === null) {
           // Use the title of the document if no name is set.
           $name = $visible_documents[$slug]
             ->getContent()
             ->getTitle();
 
           $is_interesting_name = true;
         }
       }
 
-      $uri      = new PhutilURI($link);
-      $slug     = $uri->getPath();
-      $fragment = $uri->getFragment();
-      $slug     = PhabricatorSlug::normalize($slug);
-      $slug     = PhrictionDocument::getSlugURI($slug);
-      $href     = (string)id(new PhutilURI($slug))->setFragment($fragment);
+      $uri = new PhutilURI($link);
+      $slug = $uri->getPath();
+      $slug = PhabricatorSlug::normalize($slug);
+      $slug = PhrictionDocument::getSlugURI($slug);
+
+      $anchor = idx($spec, 'anchor');
+      $href = (string)id(new PhutilURI($slug))->setFragment($anchor);
 
       $text_mode = $this->getEngine()->isTextMode();
       $mail_mode = $this->getEngine()->isHTMLMailMode();
 
       if ($this->getEngine()->getState('toc')) {
         $text = $name;
       } else if ($text_mode || $mail_mode) {
         $href = PhabricatorEnv::getProductionURI($href);
         if ($is_interesting_name) {
           $text = pht('"%s" <%s>', $name, $href);
         } else {
           $text = pht('<%s>', $href);
         }
       } else {
         if ($class === 'phriction-link-lock') {
           $name = array(
             $this->newTag(
               'i',
               array(
                 'class' => 'phui-icon-view phui-font-fa fa-lock',
               ),
               ''),
             ' ',
             $name,
           );
         }
         $text = $this->newTag(
           'a',
           array(
             'href'  => $href,
             'class' => $class,
           ),
           $name);
       }
 
       $this->getEngine()->overwriteStoredText($spec['token'], $text);
     }
   }
 
 }
diff --git a/src/infrastructure/markup/PhabricatorMarkupEngine.php b/src/infrastructure/markup/PhabricatorMarkupEngine.php
index 7c19cac57f..bb13c1d763 100644
--- a/src/infrastructure/markup/PhabricatorMarkupEngine.php
+++ b/src/infrastructure/markup/PhabricatorMarkupEngine.php
@@ -1,670 +1,670 @@
 <?php
 
 /**
  * Manages markup engine selection, configuration, application, caching and
  * pipelining.
  *
  * @{class:PhabricatorMarkupEngine} can be used to render objects which
  * implement @{interface:PhabricatorMarkupInterface} in a batched, cache-aware
  * way. For example, if you have a list of comments written in remarkup (and
  * the objects implement the correct interface) you can render them by first
  * building an engine and adding the fields with @{method:addObject}.
  *
  *   $field  = 'field:body'; // Field you want to render. Each object exposes
  *                           // one or more fields of markup.
  *
  *   $engine = new PhabricatorMarkupEngine();
  *   foreach ($comments as $comment) {
  *     $engine->addObject($comment, $field);
  *   }
  *
  * Now, call @{method:process} to perform the actual cache/rendering
  * step. This is a heavyweight call which does batched data access and
  * transforms the markup into output.
  *
  *   $engine->process();
  *
  * Finally, do something with the results:
  *
  *   $results = array();
  *   foreach ($comments as $comment) {
  *     $results[] = $engine->getOutput($comment, $field);
  *   }
  *
  * If you have a single object to render, you can use the convenience method
  * @{method:renderOneObject}.
  *
  * @task markup Markup Pipeline
  * @task engine Engine Construction
  */
 final class PhabricatorMarkupEngine extends Phobject {
 
   private $objects = array();
   private $viewer;
   private $contextObject;
-  private $version = 15;
+  private $version = 16;
   private $engineCaches = array();
   private $auxiliaryConfig = array();
 
 
 /* -(  Markup Pipeline  )---------------------------------------------------- */
 
 
   /**
    * Convenience method for pushing a single object through the markup
    * pipeline.
    *
    * @param PhabricatorMarkupInterface  The object to render.
    * @param string                      The field to render.
    * @param PhabricatorUser             User viewing the markup.
    * @param object                      A context object for policy checks
    * @return string                     Marked up output.
    * @task markup
    */
   public static function renderOneObject(
     PhabricatorMarkupInterface $object,
     $field,
     PhabricatorUser $viewer,
     $context_object = null) {
     return id(new PhabricatorMarkupEngine())
       ->setViewer($viewer)
       ->setContextObject($context_object)
       ->addObject($object, $field)
       ->process()
       ->getOutput($object, $field);
   }
 
 
   /**
    * Queue an object for markup generation when @{method:process} is
    * called. You can retrieve the output later with @{method:getOutput}.
    *
    * @param PhabricatorMarkupInterface  The object to render.
    * @param string                      The field to render.
    * @return this
    * @task markup
    */
   public function addObject(PhabricatorMarkupInterface $object, $field) {
     $key = $this->getMarkupFieldKey($object, $field);
     $this->objects[$key] = array(
       'object' => $object,
       'field'  => $field,
     );
 
     return $this;
   }
 
 
   /**
    * Process objects queued with @{method:addObject}. You can then retrieve
    * the output with @{method:getOutput}.
    *
    * @return this
    * @task markup
    */
   public function process() {
     $keys = array();
     foreach ($this->objects as $key => $info) {
       if (!isset($info['markup'])) {
         $keys[] = $key;
       }
     }
 
     if (!$keys) {
       return;
     }
 
     $objects = array_select_keys($this->objects, $keys);
 
     // Build all the markup engines. We need an engine for each field whether
     // we have a cache or not, since we still need to postprocess the cache.
     $engines = array();
     foreach ($objects as $key => $info) {
       $engines[$key] = $info['object']->newMarkupEngine($info['field']);
       $engines[$key]->setConfig('viewer', $this->viewer);
       $engines[$key]->setConfig('contextObject', $this->contextObject);
 
       foreach ($this->auxiliaryConfig as $aux_key => $aux_value) {
         $engines[$key]->setConfig($aux_key, $aux_value);
       }
     }
 
     // Load or build the preprocessor caches.
     $blocks = $this->loadPreprocessorCaches($engines, $objects);
     $blocks = mpull($blocks, 'getCacheData');
 
     $this->engineCaches = $blocks;
 
     // Finalize the output.
     foreach ($objects as $key => $info) {
       $engine = $engines[$key];
       $field = $info['field'];
       $object = $info['object'];
 
       $output = $engine->postprocessText($blocks[$key]);
       $output = $object->didMarkupText($field, $output, $engine);
       $this->objects[$key]['output'] = $output;
     }
 
     return $this;
   }
 
 
   /**
    * Get the output of markup processing for a field queued with
    * @{method:addObject}. Before you can call this method, you must call
    * @{method:process}.
    *
    * @param PhabricatorMarkupInterface  The object to retrieve.
    * @param string                      The field to retrieve.
    * @return string                     Processed output.
    * @task markup
    */
   public function getOutput(PhabricatorMarkupInterface $object, $field) {
     $key = $this->getMarkupFieldKey($object, $field);
     $this->requireKeyProcessed($key);
 
     return $this->objects[$key]['output'];
   }
 
 
   /**
    * Retrieve engine metadata for a given field.
    *
    * @param PhabricatorMarkupInterface  The object to retrieve.
    * @param string                      The field to retrieve.
    * @param string                      The engine metadata field to retrieve.
    * @param wild                        Optional default value.
    * @task markup
    */
   public function getEngineMetadata(
     PhabricatorMarkupInterface $object,
     $field,
     $metadata_key,
     $default = null) {
 
     $key = $this->getMarkupFieldKey($object, $field);
     $this->requireKeyProcessed($key);
 
     return idx($this->engineCaches[$key]['metadata'], $metadata_key, $default);
   }
 
 
   /**
    * @task markup
    */
   private function requireKeyProcessed($key) {
     if (empty($this->objects[$key])) {
       throw new Exception(
         pht(
           "Call %s before using results (key = '%s').",
           'addObject()',
           $key));
     }
 
     if (!isset($this->objects[$key]['output'])) {
       throw new PhutilInvalidStateException('process');
     }
   }
 
 
   /**
    * @task markup
    */
   private function getMarkupFieldKey(
     PhabricatorMarkupInterface $object,
     $field) {
 
     static $custom;
     if ($custom === null) {
       $custom = array_merge(
         self::loadCustomInlineRules(),
         self::loadCustomBlockRules());
 
       $custom = mpull($custom, 'getRuleVersion', null);
       ksort($custom);
       $custom = PhabricatorHash::digestForIndex(serialize($custom));
     }
 
     return $object->getMarkupFieldKey($field).'@'.$this->version.'@'.$custom;
   }
 
 
   /**
    * @task markup
    */
   private function loadPreprocessorCaches(array $engines, array $objects) {
     $blocks = array();
 
     $use_cache = array();
     foreach ($objects as $key => $info) {
       if ($info['object']->shouldUseMarkupCache($info['field'])) {
         $use_cache[$key] = true;
       }
     }
 
     if ($use_cache) {
       try {
         $blocks = id(new PhabricatorMarkupCache())->loadAllWhere(
           'cacheKey IN (%Ls)',
           array_keys($use_cache));
         $blocks = mpull($blocks, null, 'getCacheKey');
       } catch (Exception $ex) {
         phlog($ex);
       }
     }
 
     $is_readonly = PhabricatorEnv::isReadOnly();
 
     foreach ($objects as $key => $info) {
       // False check in case MySQL doesn't support unicode characters
       // in the string (T1191), resulting in unserialize returning false.
       if (isset($blocks[$key]) && $blocks[$key]->getCacheData() !== false) {
         // If we already have a preprocessing cache, we don't need to rebuild
         // it.
         continue;
       }
 
       $text = $info['object']->getMarkupText($info['field']);
       $data = $engines[$key]->preprocessText($text);
 
       // NOTE: This is just debugging information to help sort out cache issues.
       // If one machine is misconfigured and poisoning caches you can use this
       // field to hunt it down.
 
       $metadata = array(
         'host' => php_uname('n'),
       );
 
       $blocks[$key] = id(new PhabricatorMarkupCache())
         ->setCacheKey($key)
         ->setCacheData($data)
         ->setMetadata($metadata);
 
       if (isset($use_cache[$key]) && !$is_readonly) {
         // This is just filling a cache and always safe, even on a read pathway.
         $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
           $blocks[$key]->replace();
         unset($unguarded);
       }
     }
 
     return $blocks;
   }
 
 
   /**
    * Set the viewing user. Used to implement object permissions.
    *
    * @param PhabricatorUser The viewing user.
    * @return this
    * @task markup
    */
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
     return $this;
   }
 
   /**
    * Set the context object. Used to implement object permissions.
    *
    * @param The object in which context this remarkup is used.
    * @return this
    * @task markup
    */
   public function setContextObject($object) {
     $this->contextObject = $object;
     return $this;
   }
 
   public function setAuxiliaryConfig($key, $value) {
     // TODO: This is gross and should be removed. Avoid use.
     $this->auxiliaryConfig[$key] = $value;
     return $this;
   }
 
 
 /* -(  Engine Construction  )------------------------------------------------ */
 
 
 
   /**
    * @task engine
    */
   public static function newManiphestMarkupEngine() {
     return self::newMarkupEngine(array(
     ));
   }
 
 
   /**
    * @task engine
    */
   public static function newPhrictionMarkupEngine() {
     return self::newMarkupEngine(array(
       'header.generate-toc' => true,
     ));
   }
 
 
   /**
    * @task engine
    */
   public static function newPhameMarkupEngine() {
     return self::newMarkupEngine(
       array(
         'macros' => false,
         'uri.full' => true,
         'uri.same-window' => true,
         'uri.base' => PhabricatorEnv::getURI('/'),
       ));
   }
 
 
   /**
    * @task engine
    */
   public static function newFeedMarkupEngine() {
     return self::newMarkupEngine(
       array(
         'macros'      => false,
         'youtube'     => false,
       ));
   }
 
   /**
    * @task engine
    */
   public static function newCalendarMarkupEngine() {
     return self::newMarkupEngine(array(
     ));
   }
 
 
   /**
    * @task engine
    */
   public static function newDifferentialMarkupEngine(array $options = array()) {
     return self::newMarkupEngine(array(
       'differential.diff' => idx($options, 'differential.diff'),
     ));
   }
 
 
   /**
    * @task engine
    */
   public static function newDiffusionMarkupEngine(array $options = array()) {
     return self::newMarkupEngine(array(
       'header.generate-toc' => true,
     ));
   }
 
   /**
    * @task engine
    */
   public static function getEngine($ruleset = 'default') {
     static $engines = array();
     if (isset($engines[$ruleset])) {
       return $engines[$ruleset];
     }
 
     $engine = null;
     switch ($ruleset) {
       case 'default':
         $engine = self::newMarkupEngine(array());
         break;
       case 'nolinebreaks':
         $engine = self::newMarkupEngine(array());
         $engine->setConfig('preserve-linebreaks', false);
         break;
       case 'diffusion-readme':
         $engine = self::newMarkupEngine(array());
         $engine->setConfig('preserve-linebreaks', false);
         $engine->setConfig('header.generate-toc', true);
         break;
       case 'diviner':
         $engine = self::newMarkupEngine(array());
         $engine->setConfig('preserve-linebreaks', false);
   //    $engine->setConfig('diviner.renderer', new DivinerDefaultRenderer());
         $engine->setConfig('header.generate-toc', true);
         break;
       case 'extract':
         // Engine used for reference/edge extraction. Turn off anything which
         // is slow and doesn't change reference extraction.
         $engine = self::newMarkupEngine(array());
         $engine->setConfig('pygments.enabled', false);
         break;
       default:
         throw new Exception(pht('Unknown engine ruleset: %s!', $ruleset));
     }
 
     $engines[$ruleset] = $engine;
     return $engine;
   }
 
   /**
    * @task engine
    */
   private static function getMarkupEngineDefaultConfiguration() {
     return array(
       'pygments'      => PhabricatorEnv::getEnvConfig('pygments.enabled'),
       'youtube'       => PhabricatorEnv::getEnvConfig(
         'remarkup.enable-embedded-youtube'),
       'differential.diff' => null,
       'header.generate-toc' => false,
       'macros'        => true,
       'uri.allowed-protocols' => PhabricatorEnv::getEnvConfig(
         'uri.allowed-protocols'),
       'uri.full' => false,
       'syntax-highlighter.engine' => PhabricatorEnv::getEnvConfig(
         'syntax-highlighter.engine'),
       'preserve-linebreaks' => true,
     );
   }
 
 
   /**
    * @task engine
    */
   public static function newMarkupEngine(array $options) {
     $options += self::getMarkupEngineDefaultConfiguration();
 
     $engine = new PhutilRemarkupEngine();
 
     $engine->setConfig('preserve-linebreaks', $options['preserve-linebreaks']);
 
     $engine->setConfig('pygments.enabled', $options['pygments']);
     $engine->setConfig(
       'uri.allowed-protocols',
       $options['uri.allowed-protocols']);
     $engine->setConfig('differential.diff', $options['differential.diff']);
     $engine->setConfig('header.generate-toc', $options['header.generate-toc']);
     $engine->setConfig(
       'syntax-highlighter.engine',
       $options['syntax-highlighter.engine']);
 
     $style_map = id(new PhabricatorDefaultSyntaxStyle())
       ->getRemarkupStyleMap();
     $engine->setConfig('phutil.codeblock.style-map', $style_map);
 
     $engine->setConfig('uri.full', $options['uri.full']);
 
     if (isset($options['uri.base'])) {
       $engine->setConfig('uri.base', $options['uri.base']);
     }
 
     if (isset($options['uri.same-window'])) {
       $engine->setConfig('uri.same-window', $options['uri.same-window']);
     }
 
     $rules = array();
     $rules[] = new PhutilRemarkupEscapeRemarkupRule();
     $rules[] = new PhutilRemarkupMonospaceRule();
 
 
     $rules[] = new PhutilRemarkupDocumentLinkRule();
     $rules[] = new PhabricatorNavigationRemarkupRule();
 
     if ($options['youtube']) {
       $rules[] = new PhabricatorYoutubeRemarkupRule();
     }
 
     $rules[] = new PhabricatorIconRemarkupRule();
     $rules[] = new PhabricatorEmojiRemarkupRule();
     $rules[] = new PhabricatorHandleRemarkupRule();
 
     $applications = PhabricatorApplication::getAllInstalledApplications();
     foreach ($applications as $application) {
       foreach ($application->getRemarkupRules() as $rule) {
         $rules[] = $rule;
       }
     }
 
     $rules[] = new PhutilRemarkupHyperlinkRule();
 
     if ($options['macros']) {
       $rules[] = new PhabricatorImageMacroRemarkupRule();
       $rules[] = new PhabricatorMemeRemarkupRule();
     }
 
     $rules[] = new PhutilRemarkupBoldRule();
     $rules[] = new PhutilRemarkupItalicRule();
     $rules[] = new PhutilRemarkupDelRule();
     $rules[] = new PhutilRemarkupUnderlineRule();
     $rules[] = new PhutilRemarkupHighlightRule();
 
     foreach (self::loadCustomInlineRules() as $rule) {
       $rules[] = clone $rule;
     }
 
     $blocks = array();
     $blocks[] = new PhutilRemarkupQuotesBlockRule();
     $blocks[] = new PhutilRemarkupReplyBlockRule();
     $blocks[] = new PhutilRemarkupLiteralBlockRule();
     $blocks[] = new PhutilRemarkupHeaderBlockRule();
     $blocks[] = new PhutilRemarkupHorizontalRuleBlockRule();
     $blocks[] = new PhutilRemarkupListBlockRule();
     $blocks[] = new PhutilRemarkupCodeBlockRule();
     $blocks[] = new PhutilRemarkupNoteBlockRule();
     $blocks[] = new PhutilRemarkupTableBlockRule();
     $blocks[] = new PhutilRemarkupSimpleTableBlockRule();
     $blocks[] = new PhutilRemarkupInterpreterBlockRule();
     $blocks[] = new PhutilRemarkupDefaultBlockRule();
 
     foreach (self::loadCustomBlockRules() as $rule) {
       $blocks[] = $rule;
     }
 
     foreach ($blocks as $block) {
       $block->setMarkupRules($rules);
     }
 
     $engine->setBlockRules($blocks);
 
     return $engine;
   }
 
   public static function extractPHIDsFromMentions(
     PhabricatorUser $viewer,
     array $content_blocks) {
 
     $mentions = array();
 
     $engine = self::newDifferentialMarkupEngine();
     $engine->setConfig('viewer', $viewer);
 
     foreach ($content_blocks as $content_block) {
       $engine->markupText($content_block);
       $phids = $engine->getTextMetadata(
         PhabricatorMentionRemarkupRule::KEY_MENTIONED,
         array());
       $mentions += $phids;
     }
 
     return $mentions;
   }
 
   public static function extractFilePHIDsFromEmbeddedFiles(
     PhabricatorUser $viewer,
     array $content_blocks) {
     $files = array();
 
     $engine = self::newDifferentialMarkupEngine();
     $engine->setConfig('viewer', $viewer);
 
     foreach ($content_blocks as $content_block) {
       $engine->markupText($content_block);
       $phids = $engine->getTextMetadata(
         PhabricatorEmbedFileRemarkupRule::KEY_EMBED_FILE_PHIDS,
         array());
       foreach ($phids as $phid) {
         $files[$phid] = $phid;
       }
     }
 
     return array_values($files);
   }
 
   /**
    * Produce a corpus summary, in a way that shortens the underlying text
    * without truncating it somewhere awkward.
    *
    * TODO: We could do a better job of this.
    *
    * @param string  Remarkup corpus to summarize.
    * @return string Summarized corpus.
    */
   public static function summarize($corpus) {
 
     // Major goals here are:
     //  - Don't split in the middle of a character (utf-8).
     //  - Don't split in the middle of, e.g., **bold** text, since
     //    we end up with hanging '**' in the summary.
     //  - Try not to pick an image macro, header, embedded file, etc.
     //  - Hopefully don't return too much text. We don't explicitly limit
     //    this right now.
 
     $blocks = preg_split("/\n *\n\s*/", $corpus);
 
     $best = null;
     foreach ($blocks as $block) {
       // This is a test for normal spaces in the block, i.e. a heuristic to
       // distinguish standard paragraphs from things like image macros. It may
       // not work well for non-latin text. We prefer to summarize with a
       // paragraph of normal words over an image macro, if possible.
       $has_space = preg_match('/\w\s\w/', $block);
 
       // This is a test to find embedded images and headers. We prefer to
       // summarize with a normal paragraph over a header or an embedded object,
       // if possible.
       $has_embed = preg_match('/^[{=]/', $block);
 
       if ($has_space && !$has_embed) {
         // This seems like a good summary, so return it.
         return $block;
       }
 
       if (!$best) {
         // This is the first block we found; if everything is garbage just
         // use the first block.
         $best = $block;
       }
     }
 
     return $best;
   }
 
   private static function loadCustomInlineRules() {
     return id(new PhutilClassMapQuery())
       ->setAncestorClass('PhabricatorRemarkupCustomInlineRule')
       ->execute();
   }
 
   private static function loadCustomBlockRules() {
     return id(new PhutilClassMapQuery())
       ->setAncestorClass('PhabricatorRemarkupCustomBlockRule')
       ->execute();
   }
 
 }