diff --git a/scripts/symbols/generate_ctags_symbols.php b/scripts/symbols/generate_ctags_symbols.php
index 6c52521d7e..c70c408bd6 100755
--- a/scripts/symbols/generate_ctags_symbols.php
+++ b/scripts/symbols/generate_ctags_symbols.php
@@ -1,124 +1,126 @@
 #!/usr/bin/env php
 <?php
 
 $root = dirname(dirname(dirname(__FILE__)));
 require_once $root.'/scripts/__init_script__.php';
 
 if (ctags_check_executable() == false) {
   echo phutil_console_format(
     "Could not find Exuberant ctags. Make sure it is installed and\n".
     "available in executable path.\n\n".
     "Exuberant ctags project page: http://ctags.sourceforge.net/\n");
   exit(1);
 }
 
 if ($argc !== 1 || posix_isatty(STDIN)) {
   echo phutil_console_format(
     "usage: find . -type f -name '*.py' | ./generate_ctags_symbols.php\n");
   exit(1);
 }
 
 $input = file_get_contents('php://stdin');
 $input = trim($input);
 $input = explode("\n", $input);
 
 $data = array();
 $futures = array();
 
 foreach ($input as $file) {
   $file = Filesystem::readablePath($file);
   $futures[$file] = ctags_get_parser_future($file);
 }
 
-foreach (Futures($futures)->limit(8) as $file => $future) {
+$futures = id(new FutureIterator($futures))
+  ->limit(8);
+foreach ($futures as $file => $future) {
   $tags = $future->resolve();
   $tags = explode("\n", $tags[1]);
 
   foreach ($tags as $tag) {
     $parts = explode(';', $tag);
     // skip lines that we can not parse
     if (count($parts) < 2) {
       continue;
     }
 
     // split ctags information
     $tag_info = explode("\t", $parts[0]);
     // split exuberant ctags "extension fields" (additional information)
     $parts[1] = trim($parts[1], "\t \"");
     $extension_fields = explode("\t", $parts[1]);
 
     // skip lines that we can not parse
     if (count($tag_info) < 3 || count($extension_fields) < 2) {
       continue;
     }
 
     // default $context to empty
     $extension_fields[] = '';
     list($token, $file_path, $line_num) = $tag_info;
     list($type, $language, $context) = $extension_fields;
 
     // skip lines with tokens containing a space
     if (strpos($token, ' ') !== false) {
       continue;
     }
 
     // strip "language:"
     $language = substr($language, 9);
 
     // To keep consistent with "Separate with commas, for example: php, py"
     // in Arcanist Project edit form.
     $language = str_ireplace('python', 'py', $language);
 
     // also, "normalize" c++ and c#
     $language = str_ireplace('c++', 'cpp', $language);
     $language = str_ireplace('c#', 'cs', $language);
 
     // Ruby has "singleton method", for example
     $type = substr(str_replace(' ', '_', $type), 0, 12);
     // class:foo, struct:foo, union:foo, enum:foo, ...
     $context = last(explode(':', $context, 2));
 
     $ignore = array(
       'variable' => true,
     );
     if (empty($ignore[$type])) {
       print_symbol($file_path, $line_num, $type, $token, $context, $language);
     }
   }
 }
 
 function ctags_get_parser_future($file_path) {
   $future = new ExecFuture('ctags -n --fields=Kls -o - %s',
                            $file_path);
   return $future;
 }
 
 function ctags_check_executable() {
   $future = new ExecFuture('ctags --version');
   $result = $future->resolve();
 
   if (empty($result[1])) {
     return false;
   }
 
   return true;
 }
 
 function print_symbol($file, $line_num, $type, $token, $context, $language) {
   // get rid of relative path
   $file = explode('/', $file);
   if ($file[0] == '.' || $file[0] == '..') {
     array_shift($file);
   }
   $file = '/'.implode('/', $file);
 
   $parts = array(
     $context,
     $token,
     $type,
     strtolower($language),
     $line_num,
     $file,
   );
   echo implode(' ', $parts)."\n";
 }
diff --git a/scripts/symbols/generate_php_symbols.php b/scripts/symbols/generate_php_symbols.php
index 087898fdda..4129af557c 100755
--- a/scripts/symbols/generate_php_symbols.php
+++ b/scripts/symbols/generate_php_symbols.php
@@ -1,113 +1,115 @@
 #!/usr/bin/env php
 <?php
 
 $root = dirname(dirname(dirname(__FILE__)));
 require_once $root.'/scripts/__init_script__.php';
 
 if ($argc !== 1 || posix_isatty(STDIN)) {
   echo phutil_console_format(
     "usage: find . -type f -name '*.php' | ./generate_php_symbols.php\n");
   exit(1);
 }
 
 $input = file_get_contents('php://stdin');
 $input = trim($input);
 $input = explode("\n", $input);
 
 $data = array();
 $futures = array();
 
 foreach ($input as $file) {
   $file = Filesystem::readablePath($file);
   $data[$file] = Filesystem::readFile($file);
   $futures[$file] = xhpast_get_parser_future($data[$file]);
 }
 
-foreach (Futures($futures)->limit(8) as $file => $future) {
+$futures = id(new FutureIterator($futures))
+  ->limit(8);
+foreach ($futures as $file => $future) {
   $tree = XHPASTTree::newFromDataAndResolvedExecFuture(
     $data[$file],
     $future->resolve());
 
   $root = $tree->getRootNode();
   $scopes = array();
 
   $functions = $root->selectDescendantsOfType('n_FUNCTION_DECLARATION');
   foreach ($functions as $function) {
     $name = $function->getChildByIndex(2);
     // Skip anonymous functions
     if (!$name->getConcreteString()) {
       continue;
     }
     print_symbol($file, 'function', $name);
   }
 
   $classes = $root->selectDescendantsOfType('n_CLASS_DECLARATION');
   foreach ($classes as $class) {
     $class_name = $class->getChildByIndex(1);
     print_symbol($file, 'class', $class_name);
     $scopes[] = array($class, $class_name);
   }
 
   $interfaces = $root->selectDescendantsOfType('n_INTERFACE_DECLARATION');
   foreach ($interfaces as $interface) {
     $interface_name = $interface->getChildByIndex(1);
     // We don't differentiate classes and interfaces in highlighters.
     print_symbol($file, 'class', $interface_name);
     $scopes[] = array($interface, $interface_name);
   }
 
   $constants = $root->selectDescendantsOfType('n_CONSTANT_DECLARATION_LIST');
   foreach ($constants as $constant_list) {
     foreach ($constant_list->getChildren() as $constant) {
       $constant_name = $constant->getChildByIndex(0);
       print_symbol($file, 'constant', $constant_name);
     }
   }
 
   foreach ($scopes as $scope) {
     // this prints duplicate symbols in the case of nested classes
     // luckily, PHP doesn't allow those
     list($class, $class_name) = $scope;
 
     $consts = $class->selectDescendantsOfType(
       'n_CLASS_CONSTANT_DECLARATION_LIST');
     foreach ($consts as $const_list) {
       foreach ($const_list->getChildren() as $const) {
         $const_name = $const->getChildByIndex(0);
         print_symbol($file, 'class_const', $const_name, $class_name);
       }
     }
 
     $members = $class->selectDescendantsOfType(
       'n_CLASS_MEMBER_DECLARATION_LIST');
     foreach ($members as $member_list) {
       foreach ($member_list->getChildren() as $member) {
         if ($member->getTypeName() == 'n_CLASS_MEMBER_MODIFIER_LIST') {
           continue;
         }
         $member_name = $member->getChildByIndex(0);
         print_symbol($file, 'member', $member_name, $class_name);
       }
     }
 
     $methods = $class->selectDescendantsOfType('n_METHOD_DECLARATION');
     foreach ($methods as $method) {
       $method_name = $method->getChildByIndex(2);
       print_symbol($file, 'method', $method_name, $class_name);
     }
   }
 }
 
 function print_symbol($file, $type, $token, $context = null) {
   $parts = array(
     $context ? $context->getConcreteString() : '',
     // variable tokens are `$name`, not just `name`, so strip the $ off of
     // class field names
     ltrim($token->getConcreteString(), '$'),
     $type,
     'php',
     $token->getLineNumber(),
     '/'.ltrim($file, './'),
   );
   echo implode(' ', $parts)."\n";
 }
diff --git a/src/applications/differential/parser/DifferentialChangesetParser.php b/src/applications/differential/parser/DifferentialChangesetParser.php
index 9db301ab35..a27f8c823b 100644
--- a/src/applications/differential/parser/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/DifferentialChangesetParser.php
@@ -1,1297 +1,1297 @@
 <?php
 
 final class DifferentialChangesetParser {
 
   protected $visible      = array();
   protected $new          = array();
   protected $old          = array();
   protected $intra        = array();
   protected $newRender    = null;
   protected $oldRender    = null;
 
   protected $filename     = null;
   protected $hunkStartLines = array();
 
   protected $comments     = array();
   protected $specialAttributes = array();
 
   protected $changeset;
   protected $whitespaceMode = null;
 
   protected $renderCacheKey = null;
 
   private $handles = array();
   private $user;
 
   private $leftSideChangesetID;
   private $leftSideAttachesToNewFile;
 
   private $rightSideChangesetID;
   private $rightSideAttachesToNewFile;
 
   private $originalLeft;
   private $originalRight;
 
   private $renderingReference;
   private $isSubparser;
 
   private $isTopLevel;
   private $coverage;
   private $markupEngine;
   private $highlightErrors;
   private $disableCache;
   private $renderer;
   private $characterEncoding;
   private $highlightAs;
 
   public function setHighlightAs($highlight_as) {
     $this->highlightAs = $highlight_as;
     return $this;
   }
 
   public function getHighlightAs() {
     return $this->highlightAs;
   }
 
   public function setCharacterEncoding($character_encoding) {
     $this->characterEncoding = $character_encoding;
     return $this;
   }
 
   public function getCharacterEncoding() {
     return $this->characterEncoding;
   }
 
   public function setRenderer($renderer) {
     $this->renderer = $renderer;
     return $this;
   }
 
   public function getRenderer() {
     if (!$this->renderer) {
       return new DifferentialChangesetTwoUpRenderer();
     }
     return $this->renderer;
   }
 
   public function setDisableCache($disable_cache) {
     $this->disableCache = $disable_cache;
     return $this;
   }
 
   public function getDisableCache() {
     return $this->disableCache;
   }
 
   const CACHE_VERSION = 11;
   const CACHE_MAX_SIZE = 8e6;
 
   const ATTR_GENERATED  = 'attr:generated';
   const ATTR_DELETED    = 'attr:deleted';
   const ATTR_UNCHANGED  = 'attr:unchanged';
   const ATTR_WHITELINES = 'attr:white';
   const ATTR_MOVEAWAY   = 'attr:moveaway';
 
   const LINES_CONTEXT = 8;
 
   const WHITESPACE_SHOW_ALL         = 'show-all';
   const WHITESPACE_IGNORE_TRAILING  = 'ignore-trailing';
 
   // TODO: This is now "Ignore Most" in the UI.
   const WHITESPACE_IGNORE_ALL       = 'ignore-all';
 
   const WHITESPACE_IGNORE_FORCE     = 'ignore-force';
 
   public function setOldLines(array $lines) {
     $this->old = $lines;
     return $this;
   }
 
   public function setNewLines(array $lines) {
     $this->new = $lines;
     return $this;
   }
 
   public function setSpecialAttributes(array $attributes) {
     $this->specialAttributes = $attributes;
     return $this;
   }
 
   public function setIntraLineDiffs(array $diffs) {
     $this->intra = $diffs;
     return $this;
   }
 
   public function setVisibileLinesMask(array $mask) {
     $this->visible = $mask;
     return $this;
   }
 
   /**
    * Configure which Changeset comments added to the right side of the visible
    * diff will be attached to. The ID must be the ID of a real Differential
    * Changeset.
    *
    * The complexity here is that we may show an arbitrary side of an arbitrary
    * changeset as either the left or right part of a diff. This method allows
    * the left and right halves of the displayed diff to be correctly mapped to
    * storage changesets.
    *
    * @param id    The Differential Changeset ID that comments added to the right
    *              side of the visible diff should be attached to.
    * @param bool  If true, attach new comments to the right side of the storage
    *              changeset. Note that this may be false, if the left side of
    *              some storage changeset is being shown as the right side of
    *              a display diff.
    * @return this
    */
   public function setRightSideCommentMapping($id, $is_new) {
     $this->rightSideChangesetID = $id;
     $this->rightSideAttachesToNewFile = $is_new;
     return $this;
   }
 
   /**
    * See setRightSideCommentMapping(), but this sets information for the left
    * side of the display diff.
    */
   public function setLeftSideCommentMapping($id, $is_new) {
     $this->leftSideChangesetID = $id;
     $this->leftSideAttachesToNewFile = $is_new;
     return $this;
   }
 
   public function setOriginals(
     DifferentialChangeset $left,
     DifferentialChangeset $right) {
 
     $this->originalLeft = $left;
     $this->originalRight = $right;
   }
 
   public function diffOriginals() {
     $engine = new PhabricatorDifferenceEngine();
     $changeset = $engine->generateChangesetFromFileContent(
       implode('', mpull($this->originalLeft->getHunks(), 'getChanges')),
       implode('', mpull($this->originalRight->getHunks(), 'getChanges')));
 
     $parser = new DifferentialHunkParser();
 
     return $parser->parseHunksForHighlightMasks(
       $changeset->getHunks(),
       $this->originalLeft->getHunks(),
       $this->originalRight->getHunks());
   }
 
   /**
    * Set a key for identifying this changeset in the render cache. If set, the
    * parser will attempt to use the changeset render cache, which can improve
    * performance for frequently-viewed changesets.
    *
    * By default, there is no render cache key and parsers do not use the cache.
    * This is appropriate for rarely-viewed changesets.
    *
    * NOTE: Currently, this key must be a valid Differential Changeset ID.
    *
    * @param   string  Key for identifying this changeset in the render cache.
    * @return  this
    */
   public function setRenderCacheKey($key) {
     $this->renderCacheKey = $key;
     return $this;
   }
 
   private function getRenderCacheKey() {
     return $this->renderCacheKey;
   }
 
   public function setChangeset(DifferentialChangeset $changeset) {
     $this->changeset = $changeset;
 
     $this->setFilename($changeset->getFilename());
 
     return $this;
   }
 
   public function setWhitespaceMode($whitespace_mode) {
     $this->whitespaceMode = $whitespace_mode;
     return $this;
   }
 
   public function setRenderingReference($ref) {
     $this->renderingReference = $ref;
     return $this;
   }
 
   private function getRenderingReference() {
     return $this->renderingReference;
   }
 
   public function getChangeset() {
     return $this->changeset;
   }
 
   public function setFilename($filename) {
     $this->filename = $filename;
     return $this;
   }
 
   public function setHandles(array $handles) {
     assert_instances_of($handles, 'PhabricatorObjectHandle');
     $this->handles = $handles;
     return $this;
   }
 
   public function setMarkupEngine(PhabricatorMarkupEngine $engine) {
     $this->markupEngine = $engine;
     return $this;
   }
 
   public function setUser(PhabricatorUser $user) {
     $this->user = $user;
     return $this;
   }
 
   public function setCoverage($coverage) {
     $this->coverage = $coverage;
     return $this;
   }
   private function getCoverage() {
     return $this->coverage;
   }
 
   public function parseInlineComment(
     PhabricatorInlineCommentInterface $comment) {
 
     // Parse only comments which are actually visible.
     if ($this->isCommentVisibleOnRenderedDiff($comment)) {
       $this->comments[] = $comment;
     }
     return $this;
   }
 
   private function loadCache() {
     $render_cache_key = $this->getRenderCacheKey();
     if (!$render_cache_key) {
       return false;
     }
 
     $data = null;
 
     $changeset = new DifferentialChangeset();
     $conn_r = $changeset->establishConnection('r');
     $data = queryfx_one(
       $conn_r,
       'SELECT * FROM %T WHERE id = %d',
       $changeset->getTableName().'_parse_cache',
       $render_cache_key);
 
     if (!$data) {
       return false;
     }
 
     if ($data['cache'][0] == '{') {
       // This is likely an old-style JSON cache which we will not be able to
       // deserialize.
       return false;
     }
 
     $data = unserialize($data['cache']);
     if (!is_array($data) || !$data) {
       return false;
     }
 
     foreach (self::getCacheableProperties() as $cache_key) {
       if (!array_key_exists($cache_key, $data)) {
         // If we're missing a cache key, assume we're looking at an old cache
         // and ignore it.
         return false;
       }
     }
 
     if ($data['cacheVersion'] !== self::CACHE_VERSION) {
       return false;
     }
 
     // Someone displays contents of a partially cached shielded file.
     if (!isset($data['newRender']) && (!$this->isTopLevel || $this->comments)) {
       return false;
     }
 
     unset($data['cacheVersion'], $data['cacheHost']);
     $cache_prop = array_select_keys($data, self::getCacheableProperties());
     foreach ($cache_prop as $cache_key => $v) {
       $this->$cache_key = $v;
     }
 
     return true;
   }
 
   protected static function getCacheableProperties() {
     return array(
       'visible',
       'new',
       'old',
       'intra',
       'newRender',
       'oldRender',
       'specialAttributes',
       'hunkStartLines',
       'cacheVersion',
       'cacheHost',
     );
   }
 
   public function saveCache() {
     if ($this->highlightErrors) {
       return false;
     }
 
     $render_cache_key = $this->getRenderCacheKey();
     if (!$render_cache_key) {
       return false;
     }
 
     $cache = array();
     foreach (self::getCacheableProperties() as $cache_key) {
       switch ($cache_key) {
         case 'cacheVersion':
           $cache[$cache_key] = self::CACHE_VERSION;
           break;
         case 'cacheHost':
           $cache[$cache_key] = php_uname('n');
           break;
         default:
           $cache[$cache_key] = $this->$cache_key;
           break;
       }
     }
     $cache = serialize($cache);
 
     // We don't want to waste too much space by a single changeset.
     if (strlen($cache) > self::CACHE_MAX_SIZE) {
       return;
     }
 
     $changeset = new DifferentialChangeset();
     $conn_w = $changeset->establishConnection('w');
 
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
       try {
         queryfx(
           $conn_w,
           'INSERT INTO %T (id, cache, dateCreated) VALUES (%d, %B, %d)
             ON DUPLICATE KEY UPDATE cache = VALUES(cache)',
           DifferentialChangeset::TABLE_CACHE,
           $render_cache_key,
           $cache,
           time());
       } catch (AphrontQueryException $ex) {
         // Ignore these exceptions. A common cause is that the cache is
         // larger than 'max_allowed_packet', in which case we're better off
         // not writing it.
 
         // TODO: It would be nice to tailor this more narrowly.
       }
     unset($unguarded);
   }
 
   private function markGenerated($new_corpus_block = '') {
     $generated_guess = (strpos($new_corpus_block, '@'.'generated') !== false);
 
     if (!$generated_guess) {
       $generated_path_regexps = PhabricatorEnv::getEnvConfig(
         'differential.generated-paths');
       foreach ($generated_path_regexps as $regexp) {
         if (preg_match($regexp, $this->changeset->getFilename())) {
           $generated_guess = true;
           break;
         }
       }
     }
 
     $event = new PhabricatorEvent(
       PhabricatorEventType::TYPE_DIFFERENTIAL_WILLMARKGENERATED,
       array(
         'corpus' => $new_corpus_block,
         'is_generated' => $generated_guess,
       )
     );
     PhutilEventEngine::dispatchEvent($event);
 
     $generated = $event->getValue('is_generated');
     $this->specialAttributes[self::ATTR_GENERATED] = $generated;
   }
 
   public function isGenerated() {
     return idx($this->specialAttributes, self::ATTR_GENERATED, false);
   }
 
   public function isDeleted() {
     return idx($this->specialAttributes, self::ATTR_DELETED, false);
   }
 
   public function isUnchanged() {
     return idx($this->specialAttributes, self::ATTR_UNCHANGED, false);
   }
 
   public function isWhitespaceOnly() {
     return idx($this->specialAttributes, self::ATTR_WHITELINES, false);
   }
 
   public function isMoveAway() {
     return idx($this->specialAttributes, self::ATTR_MOVEAWAY, false);
   }
 
   private function applyIntraline(&$render, $intra, $corpus) {
 
     foreach ($render as $key => $text) {
       if (isset($intra[$key])) {
         $render[$key] = ArcanistDiffUtils::applyIntralineDiff(
           $text,
           $intra[$key]);
       }
     }
   }
 
   private function getHighlightFuture($corpus) {
     $language = $this->highlightAs;
 
     if (!$language) {
       $language = $this->highlightEngine->getLanguageFromFilename(
         $this->filename);
     }
 
     return $this->highlightEngine->getHighlightFuture(
       $language,
       $corpus);
   }
 
   protected function processHighlightedSource($data, $result) {
 
     $result_lines = phutil_split_lines($result);
     foreach ($data as $key => $info) {
       if (!$info) {
         unset($result_lines[$key]);
       }
     }
     return $result_lines;
   }
 
   private function tryCacheStuff() {
     $whitespace_mode = $this->whitespaceMode;
     switch ($whitespace_mode) {
       case self::WHITESPACE_SHOW_ALL:
       case self::WHITESPACE_IGNORE_TRAILING:
       case self::WHITESPACE_IGNORE_FORCE:
         break;
       default:
         $whitespace_mode = self::WHITESPACE_IGNORE_ALL;
         break;
     }
 
     $skip_cache = ($whitespace_mode != self::WHITESPACE_IGNORE_ALL);
     if ($this->disableCache) {
       $skip_cache = true;
     }
 
     if ($this->characterEncoding) {
       $skip_cache = true;
     }
 
     if ($this->highlightAs) {
       $skip_cache = true;
     }
 
     $this->whitespaceMode = $whitespace_mode;
 
     $changeset = $this->changeset;
 
     if ($changeset->getFileType() != DifferentialChangeType::FILE_TEXT &&
         $changeset->getFileType() != DifferentialChangeType::FILE_SYMLINK) {
 
       $this->markGenerated();
 
     } else {
       if ($skip_cache || !$this->loadCache()) {
         $this->process();
         if (!$skip_cache) {
           $this->saveCache();
         }
       }
     }
   }
 
   private function process() {
     $whitespace_mode = $this->whitespaceMode;
     $changeset = $this->changeset;
 
     $ignore_all = (($whitespace_mode == self::WHITESPACE_IGNORE_ALL) ||
                   ($whitespace_mode == self::WHITESPACE_IGNORE_FORCE));
 
     $force_ignore = ($whitespace_mode == self::WHITESPACE_IGNORE_FORCE);
 
     if (!$force_ignore) {
       if ($ignore_all && $changeset->getWhitespaceMatters()) {
         $ignore_all = false;
       }
     }
 
     // The "ignore all whitespace" algorithm depends on rediffing the
     // files, and we currently need complete representations of both
     // files to do anything reasonable. If we only have parts of the files,
     // don't use the "ignore all" algorithm.
     if ($ignore_all) {
       $hunks = $changeset->getHunks();
       if (count($hunks) !== 1) {
         $ignore_all = false;
       } else {
         $first_hunk = reset($hunks);
         if ($first_hunk->getOldOffset() != 1 ||
             $first_hunk->getNewOffset() != 1) {
             $ignore_all = false;
         }
       }
     }
 
     if ($ignore_all) {
       $old_file = $changeset->makeOldFile();
       $new_file = $changeset->makeNewFile();
       if ($old_file == $new_file) {
         // If the old and new files are exactly identical, the synthetic
         // diff below will give us nonsense and whitespace modes are
         // irrelevant anyway. This occurs when you, e.g., copy a file onto
         // itself in Subversion (see T271).
         $ignore_all = false;
       }
     }
 
     $hunk_parser = new DifferentialHunkParser();
     $hunk_parser->setWhitespaceMode($whitespace_mode);
     $hunk_parser->parseHunksForLineData($changeset->getHunks());
 
     // Depending on the whitespace mode, we may need to compute a different
     // set of changes than the set of changes in the hunk data (specificaly,
     // we might want to consider changed lines which have only whitespace
     // changes as unchanged).
     if ($ignore_all) {
       $engine = new PhabricatorDifferenceEngine();
       $engine->setIgnoreWhitespace(true);
       $no_whitespace_changeset = $engine->generateChangesetFromFileContent(
         $old_file,
         $new_file);
 
       $type_parser = new DifferentialHunkParser();
       $type_parser->parseHunksForLineData($no_whitespace_changeset->getHunks());
 
       $hunk_parser->setOldLineTypeMap($type_parser->getOldLineTypeMap());
       $hunk_parser->setNewLineTypeMap($type_parser->getNewLineTypeMap());
     }
 
     $hunk_parser->reparseHunksForSpecialAttributes();
 
     $unchanged = false;
     if (!$hunk_parser->getHasAnyChanges()) {
       $filetype = $this->changeset->getFileType();
       if ($filetype == DifferentialChangeType::FILE_TEXT ||
           $filetype == DifferentialChangeType::FILE_SYMLINK) {
         $unchanged = true;
       }
     }
 
     $moveaway = false;
     $changetype = $this->changeset->getChangeType();
     if ($changetype == DifferentialChangeType::TYPE_MOVE_AWAY) {
       // sometimes we show moved files as unchanged, sometimes deleted,
       // and sometimes inconsistent with what actually happened at the
       // destination of the move. Rather than make a false claim,
       // omit the 'not changed' notice if this is the source of a move
       $unchanged = false;
       $moveaway = true;
     }
 
     $this->setSpecialAttributes(array(
       self::ATTR_UNCHANGED  => $unchanged,
       self::ATTR_DELETED    => $hunk_parser->getIsDeleted(),
       self::ATTR_WHITELINES => !$hunk_parser->getHasTextChanges(),
       self::ATTR_MOVEAWAY   => $moveaway,
     ));
 
     $hunk_parser->generateIntraLineDiffs();
     $hunk_parser->generateVisibileLinesMask();
 
     $this->setOldLines($hunk_parser->getOldLines());
     $this->setNewLines($hunk_parser->getNewLines());
     $this->setIntraLineDiffs($hunk_parser->getIntraLineDiffs());
     $this->setVisibileLinesMask($hunk_parser->getVisibleLinesMask());
     $this->hunkStartLines = $hunk_parser->getHunkStartLines(
       $changeset->getHunks());
 
     $new_corpus = $hunk_parser->getNewCorpus();
     $new_corpus_block = implode('', $new_corpus);
     $this->markGenerated($new_corpus_block);
 
     if ($this->isTopLevel &&
         !$this->comments &&
           ($this->isGenerated() ||
            $this->isUnchanged() ||
            $this->isDeleted())) {
       return;
     }
 
     $old_corpus = $hunk_parser->getOldCorpus();
     $old_corpus_block = implode('', $old_corpus);
     $old_future = $this->getHighlightFuture($old_corpus_block);
     $new_future = $this->getHighlightFuture($new_corpus_block);
     $futures = array(
       'old' => $old_future,
       'new' => $new_future,
     );
     $corpus_blocks = array(
       'old' => $old_corpus_block,
       'new' => $new_corpus_block,
     );
 
     $this->highlightErrors = false;
-    foreach (Futures($futures) as $key => $future) {
+    foreach (new FutureIterator($futures) as $key => $future) {
       try {
         try {
           $highlighted = $future->resolve();
         } catch (PhutilSyntaxHighlighterException $ex) {
           $this->highlightErrors = true;
           $highlighted = id(new PhutilDefaultSyntaxHighlighter())
             ->getHighlightFuture($corpus_blocks[$key])
             ->resolve();
         }
         switch ($key) {
         case 'old':
           $this->oldRender = $this->processHighlightedSource(
             $this->old,
             $highlighted);
           break;
         case 'new':
           $this->newRender = $this->processHighlightedSource(
             $this->new,
             $highlighted);
           break;
         }
       } catch (Exception $ex) {
         phlog($ex);
         throw $ex;
       }
     }
 
     $this->applyIntraline(
       $this->oldRender,
       ipull($this->intra, 0),
       $old_corpus);
     $this->applyIntraline(
       $this->newRender,
       ipull($this->intra, 1),
       $new_corpus);
   }
 
   private function shouldRenderPropertyChangeHeader($changeset) {
     if (!$this->isTopLevel) {
       // We render properties only at top level; otherwise we get multiple
       // copies of them when a user clicks "Show More".
       return false;
     }
 
     return true;
   }
 
   public function render(
     $range_start  = null,
     $range_len    = null,
     $mask_force   = array()) {
 
     // "Top level" renders are initial requests for the whole file, versus
     // requests for a specific range generated by clicking "show more". We
     // generate property changes and "shield" UI elements only for toplevel
     // requests.
     $this->isTopLevel = (($range_start === null) && ($range_len === null));
     $this->highlightEngine = PhabricatorSyntaxHighlighter::newEngine();
 
     $encoding = null;
     if ($this->characterEncoding) {
       // We are forcing this changeset to be interpreted with a specific
       // character encoding, so force all the hunks into that encoding and
       // propagate it to the renderer.
       $encoding = $this->characterEncoding;
       foreach ($this->changeset->getHunks() as $hunk) {
         $hunk->forceEncoding($this->characterEncoding);
       }
     } else {
       // We're just using the default, so tell the renderer what that is
       // (by reading the encoding from the first hunk).
       foreach ($this->changeset->getHunks() as $hunk) {
         $encoding = $hunk->getDataEncoding();
         break;
       }
     }
 
     $this->tryCacheStuff();
     $render_pch = $this->shouldRenderPropertyChangeHeader($this->changeset);
 
     $rows = max(
       count($this->old),
       count($this->new));
 
     $renderer = $this->getRenderer()
       ->setChangeset($this->changeset)
       ->setRenderPropertyChangeHeader($render_pch)
       ->setIsTopLevel($this->isTopLevel)
       ->setOldRender($this->oldRender)
       ->setNewRender($this->newRender)
       ->setHunkStartLines($this->hunkStartLines)
       ->setOldChangesetID($this->leftSideChangesetID)
       ->setNewChangesetID($this->rightSideChangesetID)
       ->setOldAttachesToNewFile($this->leftSideAttachesToNewFile)
       ->setNewAttachesToNewFile($this->rightSideAttachesToNewFile)
       ->setCodeCoverage($this->getCoverage())
       ->setRenderingReference($this->getRenderingReference())
       ->setMarkupEngine($this->markupEngine)
       ->setHandles($this->handles)
       ->setOldLines($this->old)
       ->setNewLines($this->new)
       ->setOriginalCharacterEncoding($encoding);
 
     if ($this->user) {
       $renderer->setUser($this->user);
     }
 
     $shield = null;
     if ($this->isTopLevel && !$this->comments) {
       if ($this->isGenerated()) {
         $shield = $renderer->renderShield(
           pht(
             'This file contains generated code, which does not normally '.
             'need to be reviewed.'));
       } else if ($this->isUnchanged()) {
         $type = 'text';
         if (!$rows) {
           // NOTE: Normally, diffs which don't change files do not include
           // file content (for example, if you "chmod +x" a file and then
           // run "git show", the file content is not available). Similarly,
           // if you move a file from A to B without changing it, diffs normally
           // do not show the file content. In some cases `arc` is able to
           // synthetically generate content for these diffs, but for raw diffs
           // we'll never have it so we need to be prepared to not render a link.
           $type = 'none';
         }
         $shield = $renderer->renderShield(
           pht('The contents of this file were not changed.'),
           $type);
       } else if ($this->isMoveAway()) {
         $shield = null;
       } else if ($this->isWhitespaceOnly()) {
         $shield = $renderer->renderShield(
           pht('This file was changed only by adding or removing whitespace.'),
           'whitespace');
       } else if ($this->isDeleted()) {
         $shield = $renderer->renderShield(
           pht('This file was completely deleted.'));
       } else if ($this->changeset->getAffectedLineCount() > 2500) {
         $lines = number_format($this->changeset->getAffectedLineCount());
         $shield = $renderer->renderShield(
           pht(
             'This file has a very large number of changes (%s lines).',
             $lines));
       }
     }
 
     if ($shield) {
       return $renderer->renderChangesetTable($shield);
     }
 
     $old_comments = array();
     $new_comments = array();
     $old_mask = array();
     $new_mask = array();
     $feedback_mask = array();
 
     if ($this->comments) {
       foreach ($this->comments as $comment) {
         $start = max($comment->getLineNumber() - self::LINES_CONTEXT, 0);
         $end = $comment->getLineNumber() +
           $comment->getLineLength() +
           self::LINES_CONTEXT;
         $new_side = $this->isCommentOnRightSideWhenDisplayed($comment);
         for ($ii = $start; $ii <= $end; $ii++) {
           if ($new_side) {
             $new_mask[$ii] = true;
           } else {
             $old_mask[$ii] = true;
           }
         }
       }
 
       foreach ($this->old as $ii => $old) {
         if (isset($old['line']) && isset($old_mask[$old['line']])) {
           $feedback_mask[$ii] = true;
         }
       }
 
       foreach ($this->new as $ii => $new) {
         if (isset($new['line']) && isset($new_mask[$new['line']])) {
           $feedback_mask[$ii] = true;
         }
       }
       $this->comments = msort($this->comments, 'getID');
       foreach ($this->comments as $comment) {
         $final = $comment->getLineNumber() +
           $comment->getLineLength();
         $final = max(1, $final);
         if ($this->isCommentOnRightSideWhenDisplayed($comment)) {
           $new_comments[$final][] = $comment;
         } else {
           $old_comments[$final][] = $comment;
         }
       }
     }
     $renderer
       ->setOldComments($old_comments)
       ->setNewComments($new_comments);
 
     switch ($this->changeset->getFileType()) {
       case DifferentialChangeType::FILE_IMAGE:
         $old = null;
         $new = null;
         // TODO: Improve the architectural issue as discussed in D955
         // https://secure.phabricator.com/D955
         $reference = $this->getRenderingReference();
         $parts = explode('/', $reference);
         if (count($parts) == 2) {
           list($id, $vs) = $parts;
         } else {
           $id = $parts[0];
           $vs = 0;
         }
         $id = (int)$id;
         $vs = (int)$vs;
 
         if (!$vs) {
           $metadata = $this->changeset->getMetadata();
           $data = idx($metadata, 'attachment-data');
 
           $old_phid = idx($metadata, 'old:binary-phid');
           $new_phid = idx($metadata, 'new:binary-phid');
         } else {
           $vs_changeset = id(new DifferentialChangeset())->load($vs);
           $old_phid = null;
           $new_phid = null;
 
           // TODO: This is spooky, see D6851
           if ($vs_changeset) {
             $vs_metadata = $vs_changeset->getMetadata();
             $old_phid = idx($vs_metadata, 'new:binary-phid');
           }
 
           $changeset = id(new DifferentialChangeset())->load($id);
           if ($changeset) {
             $metadata = $changeset->getMetadata();
             $new_phid = idx($metadata, 'new:binary-phid');
           }
         }
 
         if ($old_phid || $new_phid) {
           // grab the files, (micro) optimization for 1 query not 2
           $file_phids = array();
           if ($old_phid) {
             $file_phids[] = $old_phid;
           }
           if ($new_phid) {
             $file_phids[] = $new_phid;
           }
 
           // TODO: (T603) Probably fine to use omnipotent viewer here?
           $files = id(new PhabricatorFile())->loadAllWhere(
             'phid IN (%Ls)',
             $file_phids);
           foreach ($files as $file) {
             if (empty($file)) {
               continue;
             }
             if ($file->getPHID() == $old_phid) {
               $old = $file;
             } else if ($file->getPHID() == $new_phid) {
               $new = $file;
             }
           }
         }
 
         $renderer->attachOldFile($old);
         $renderer->attachNewFile($new);
 
         return $renderer->renderFileChange($old, $new, $id, $vs);
       case DifferentialChangeType::FILE_DIRECTORY:
       case DifferentialChangeType::FILE_BINARY:
         $output = $renderer->renderChangesetTable(null);
         return $output;
     }
 
     if ($this->originalLeft && $this->originalRight) {
       list($highlight_old, $highlight_new) = $this->diffOriginals();
       $highlight_old = array_flip($highlight_old);
       $highlight_new = array_flip($highlight_new);
       $renderer
         ->setHighlightOld($highlight_old)
         ->setHighlightNew($highlight_new);
     }
     $renderer
       ->setOriginalOld($this->originalLeft)
       ->setOriginalNew($this->originalRight);
 
     if ($range_start === null) {
       $range_start = 0;
     }
     if ($range_len === null) {
       $range_len = $rows;
     }
     $range_len = min($range_len, $rows - $range_start);
 
     list($gaps, $mask, $depths) = $this->calculateGapsMaskAndDepths(
       $mask_force,
       $feedback_mask,
       $range_start,
       $range_len);
 
     $renderer
       ->setGaps($gaps)
       ->setMask($mask)
       ->setDepths($depths);
 
     $html = $renderer->renderTextChange(
       $range_start,
       $range_len,
       $rows);
 
     return $renderer->renderChangesetTable($html);
   }
 
   /**
    * This function calculates a lot of stuff we need to know to display
    * the diff:
    *
    * Gaps - compute gaps in the visible display diff, where we will render
    * "Show more context" spacers. If a gap is smaller than the context size,
    * we just display it. Otherwise, we record it into $gaps and will render a
    * "show more context" element instead of diff text below. A given $gap
    * is a tuple of $gap_line_number_start and $gap_length.
    *
    * Mask - compute the actual lines that need to be shown (because they
    * are near changes lines, near inline comments, or the request has
    * explicitly asked for them, i.e. resulting from the user clicking
    * "show more"). The $mask returned is a sparesely populated dictionary
    * of $visible_line_number => true.
    *
    * Depths - compute how indented any given line is. The $depths returned
    * is a sparesely populated dictionary of $visible_line_number => $depth.
    *
    * This function also has the side effect of modifying member variable
    * new such that tabs are normalized to spaces for each line of the diff.
    *
    * @return array($gaps, $mask, $depths)
    */
   private function calculateGapsMaskAndDepths($mask_force,
                                               $feedback_mask,
                                               $range_start,
                                               $range_len) {
 
     // Calculate gaps and mask first
     $gaps = array();
     $gap_start = 0;
     $in_gap = false;
     $base_mask = $this->visible + $mask_force + $feedback_mask;
     $base_mask[$range_start + $range_len] = true;
     for ($ii = $range_start; $ii <= $range_start + $range_len; $ii++) {
       if (isset($base_mask[$ii])) {
         if ($in_gap) {
           $gap_length = $ii - $gap_start;
           if ($gap_length <= self::LINES_CONTEXT) {
             for ($jj = $gap_start; $jj <= $gap_start + $gap_length; $jj++) {
               $base_mask[$jj] = true;
             }
           } else {
             $gaps[] = array($gap_start, $gap_length);
           }
           $in_gap = false;
         }
       } else {
         if (!$in_gap) {
           $gap_start = $ii;
           $in_gap = true;
         }
       }
     }
     $gaps = array_reverse($gaps);
     $mask = $base_mask;
 
     // Time to calculate depth.
     // We need to go backwards to properly indent whitespace in this code:
     //
     //   0: class C {
     //   1:
     //   1:   function f() {
     //   2:
     //   2:     return;
     //   1:
     //   1:   }
     //   0:
     //   0: }
     //
     $depths = array();
     $last_depth = 0;
     $range_end = $range_start + $range_len;
     if (!isset($this->new[$range_end])) {
       $range_end--;
     }
     for ($ii = $range_end; $ii >= $range_start; $ii--) {
       // We need to expand tabs to process mixed indenting and to round
       // correctly later.
       $line = str_replace("\t", '  ', $this->new[$ii]['text']);
       $trimmed = ltrim($line);
       if ($trimmed != '') {
         // We round down to flatten "/**" and " *".
         $last_depth = floor((strlen($line) - strlen($trimmed)) / 2);
       }
       $depths[$ii] = $last_depth;
     }
 
     return array($gaps, $mask, $depths);
   }
 
   /**
    * Determine if an inline comment will appear on the rendered diff,
    * taking into consideration which halves of which changesets will actually
    * be shown.
    *
    * @param PhabricatorInlineCommentInterface Comment to test for visibility.
    * @return bool True if the comment is visible on the rendered diff.
    */
   private function isCommentVisibleOnRenderedDiff(
     PhabricatorInlineCommentInterface $comment) {
 
     $changeset_id = $comment->getChangesetID();
     $is_new = $comment->getIsNewFile();
 
     if ($changeset_id == $this->rightSideChangesetID &&
         $is_new == $this->rightSideAttachesToNewFile) {
         return true;
     }
 
     if ($changeset_id == $this->leftSideChangesetID &&
         $is_new == $this->leftSideAttachesToNewFile) {
         return true;
     }
 
     return false;
   }
 
 
   /**
    * Determine if a comment will appear on the right side of the display diff.
    * Note that the comment must appear somewhere on the rendered changeset, as
    * per isCommentVisibleOnRenderedDiff().
    *
    * @param PhabricatorInlineCommentInterface Comment to test for display
    *              location.
    * @return bool True for right, false for left.
    */
   private function isCommentOnRightSideWhenDisplayed(
     PhabricatorInlineCommentInterface $comment) {
 
     if (!$this->isCommentVisibleOnRenderedDiff($comment)) {
       throw new Exception('Comment is not visible on changeset!');
     }
 
     $changeset_id = $comment->getChangesetID();
     $is_new = $comment->getIsNewFile();
 
     if ($changeset_id == $this->rightSideChangesetID &&
         $is_new == $this->rightSideAttachesToNewFile) {
       return true;
     }
 
     return false;
   }
 
   /**
    * Parse the 'range' specification that this class and the client-side JS
    * emit to indicate that a user clicked "Show more..." on a diff. Generally,
    * use is something like this:
    *
    *   $spec = $request->getStr('range');
    *   $parsed = DifferentialChangesetParser::parseRangeSpecification($spec);
    *   list($start, $end, $mask) = $parsed;
    *   $parser->render($start, $end, $mask);
    *
    * @param string Range specification, indicating the range of the diff that
    *               should be rendered.
    * @return tuple List of <start, end, mask> suitable for passing to
    *               @{method:render}.
    */
   public static function parseRangeSpecification($spec) {
     $range_s = null;
     $range_e = null;
     $mask = array();
 
     if ($spec) {
       $match = null;
       if (preg_match('@^(\d+)-(\d+)(?:/(\d+)-(\d+))?$@', $spec, $match)) {
         $range_s = (int)$match[1];
         $range_e = (int)$match[2];
         if (count($match) > 3) {
           $start = (int)$match[3];
           $len = (int)$match[4];
           for ($ii = $start; $ii < $start + $len; $ii++) {
             $mask[$ii] = true;
           }
         }
       }
     }
 
     return array($range_s, $range_e, $mask);
   }
 
   /**
    * Render "modified coverage" information; test coverage on modified lines.
    * This synthesizes diff information with unit test information into a useful
    * indicator of how well tested a change is.
    */
   public function renderModifiedCoverage() {
     $na = phutil_tag('em', array(), '-');
 
     $coverage = $this->getCoverage();
     if (!$coverage) {
       return $na;
     }
 
     $covered = 0;
     $not_covered = 0;
 
     foreach ($this->new as $k => $new) {
       if (!$new['line']) {
         continue;
       }
 
       if (!$new['type']) {
         continue;
       }
 
       if (empty($coverage[$new['line'] - 1])) {
         continue;
       }
 
       switch ($coverage[$new['line'] - 1]) {
         case 'C':
           $covered++;
           break;
         case 'U':
           $not_covered++;
           break;
       }
     }
 
     if (!$covered && !$not_covered) {
       return $na;
     }
 
     return sprintf('%d%%', 100 * ($covered / ($covered + $not_covered)));
   }
 
   public function detectCopiedCode(
     array $changesets,
     $min_width = 30,
     $min_lines = 3) {
 
     assert_instances_of($changesets, 'DifferentialChangeset');
 
     $map = array();
     $files = array();
     $types = array();
     foreach ($changesets as $changeset) {
       $file = $changeset->getFilename();
       foreach ($changeset->getHunks() as $hunk) {
         $line = $hunk->getOldOffset();
         foreach (explode("\n", $hunk->getChanges()) as $code) {
           $type = (isset($code[0]) ? $code[0] : '');
           if ($type == '-' || $type == ' ') {
             $code = trim(substr($code, 1));
             $files[$file][$line] = $code;
             $types[$file][$line] = $type;
             if (strlen($code) >= $min_width) {
               $map[$code][] = array($file, $line);
             }
             $line++;
           }
         }
       }
     }
 
     foreach ($changesets as $changeset) {
       $copies = array();
       foreach ($changeset->getHunks() as $hunk) {
         $added = array_map('trim', $hunk->getAddedLines());
         for (reset($added); list($line, $code) = each($added); ) {
           if (isset($map[$code])) { // We found a long matching line.
 
             if (count($map[$code]) > 16) {
               // If there are a large number of identical lines in this diff,
               // don't try to figure out where this block came from: the
               // analysis is O(N^2), since we need to compare every line
               // against every other line. Even if we arrive at a result, it
               // is unlikely to be meaningful. See T5041.
               continue 2;
             }
 
             $best_length = 0;
             foreach ($map[$code] as $val) { // Explore all candidates.
               list($file, $orig_line) = $val;
               $length = 1;
               // Search also backwards for short lines.
               foreach (array(-1, 1) as $direction) {
                 $offset = $direction;
                 while (!isset($copies[$line + $offset]) &&
                     isset($added[$line + $offset]) &&
                     idx($files[$file], $orig_line + $offset) ===
                       $added[$line + $offset]) {
                   $length++;
                   $offset += $direction;
                 }
               }
               if ($length > $best_length ||
                   ($length == $best_length && // Prefer moves.
                    idx($types[$file], $orig_line) == '-')) {
                 $best_length = $length;
                 // ($offset - 1) contains number of forward matching lines.
                 $best_offset = $offset - 1;
                 $best_file = $file;
                 $best_line = $orig_line;
               }
             }
             $file = ($best_file == $changeset->getFilename() ? '' : $best_file);
             for ($i = $best_length; $i--; ) {
               $type = idx($types[$best_file], $best_line + $best_offset - $i);
               $copies[$line + $best_offset - $i] = ($best_length < $min_lines
                 ? array() // Ignore short blocks.
                 : array($file, $best_line + $best_offset - $i, $type));
             }
             for ($i = 0; $i < $best_offset; $i++) {
               next($added);
             }
           }
         }
       }
       $copies = array_filter($copies);
       if ($copies) {
         $metadata = $changeset->getMetadata();
         $metadata['copy:lines'] = $copies;
         $changeset->setMetadata($metadata);
       }
     }
     return $changesets;
   }
 
 }
diff --git a/src/applications/diffusion/DiffusionLintSaveRunner.php b/src/applications/diffusion/DiffusionLintSaveRunner.php
index 23bc70a2ef..6adcde8dda 100644
--- a/src/applications/diffusion/DiffusionLintSaveRunner.php
+++ b/src/applications/diffusion/DiffusionLintSaveRunner.php
@@ -1,289 +1,291 @@
 <?php
 
 final class DiffusionLintSaveRunner {
   private $arc = 'arc';
   private $severity = ArcanistLintSeverity::SEVERITY_ADVICE;
   private $all = false;
   private $chunkSize = 256;
   private $needsBlame = false;
 
   private $svnRoot;
   private $lintCommit;
   private $branch;
   private $conn;
   private $deletes = array();
   private $inserts = array();
   private $blame = array();
 
 
   public function setArc($path) {
     $this->arc = $path;
     return $this;
   }
 
   public function setSeverity($string) {
     $this->severity = $string;
     return $this;
   }
 
   public function setAll($bool) {
     $this->all = $bool;
     return $this;
   }
 
   public function setChunkSize($number) {
     $this->chunkSize = $number;
     return $this;
   }
 
   public function setNeedsBlame($boolean) {
     $this->needsBlame = $boolean;
     return $this;
   }
 
 
   public function run($dir) {
     $working_copy = ArcanistWorkingCopyIdentity::newFromPath($dir);
     $configuration_manager = new ArcanistConfigurationManager();
     $configuration_manager->setWorkingCopyIdentity($working_copy);
     $api = ArcanistRepositoryAPI::newAPIFromConfigurationManager(
       $configuration_manager);
 
     $this->svnRoot = id(new PhutilURI($api->getSourceControlPath()))->getPath();
     if ($api instanceof ArcanistGitAPI) {
       $svn_fetch = $api->getGitConfig('svn-remote.svn.fetch');
       list($this->svnRoot) = explode(':', $svn_fetch);
       if ($this->svnRoot != '') {
         $this->svnRoot = '/'.$this->svnRoot;
       }
     }
 
     $project_id = $working_copy->getProjectID();
     $project = id(new PhabricatorRepositoryArcanistProject())
       ->loadOneWhere('name = %s', $project_id);
     if (!$project || !$project->getRepositoryID()) {
       throw new Exception("Couldn't find repository for {$project_id}.");
     }
 
     $branch_name = $api->getBranchName();
 
     $this->branch = PhabricatorRepositoryBranch::loadOrCreateBranch(
       $project->getRepositoryID(),
       $branch_name);
     $this->conn = $this->branch->establishConnection('w');
 
     $this->lintCommit = null;
     if (!$this->all) {
       $this->lintCommit = $this->branch->getLintCommit();
     }
 
     if ($this->lintCommit) {
       try {
         $commit = $this->lintCommit;
         if ($this->svnRoot) {
           $commit = $api->getCanonicalRevisionName('@'.$commit);
         }
         $all_files = $api->getChangedFiles($commit);
       } catch (ArcanistCapabilityNotSupportedException $ex) {
         $this->lintCommit = null;
       }
     }
 
 
     if (!$this->lintCommit) {
       $where = ($this->svnRoot
         ? qsprintf($this->conn, 'AND path LIKE %>', $this->svnRoot.'/')
         : '');
       queryfx(
         $this->conn,
         'DELETE FROM %T WHERE branchID = %d %Q',
         PhabricatorRepository::TABLE_LINTMESSAGE,
         $this->branch->getID(),
         $where);
       $all_files = $api->getAllFiles();
     }
 
     $count = 0;
 
     $files = array();
     foreach ($all_files as $file => $val) {
       $count++;
       if (!$this->lintCommit) {
         $file = $val;
       } else {
         $this->deletes[] = $this->svnRoot.'/'.$file;
         if ($val & ArcanistRepositoryAPI::FLAG_DELETED) {
           continue;
         }
       }
       $files[$file] = $file;
 
       if (count($files) >= $this->chunkSize) {
         $this->runArcLint($files);
         $files = array();
       }
     }
 
     $this->runArcLint($files);
     $this->saveLintMessages();
 
     $this->lintCommit = $api->getUnderlyingWorkingCopyRevision();
     $this->branch->setLintCommit($this->lintCommit);
     $this->branch->save();
 
     if ($this->blame) {
       $this->blameAuthors();
       $this->blame = array();
     }
 
     return $count;
   }
 
 
   private function runArcLint(array $files) {
     if (!$files) {
       return;
     }
 
     echo '.';
     try {
       $future = new ExecFuture(
         '%C lint --severity %s --output json %Ls',
         $this->arc,
         $this->severity,
         $files);
 
       foreach (new LinesOfALargeExecFuture($future) as $json) {
         $paths = json_decode($json, true);
         if (!is_array($paths)) {
           fprintf(STDERR, "Invalid JSON: {$json}\n");
           continue;
         }
 
         foreach ($paths as $path => $messages) {
           if (!isset($files[$path])) {
             continue;
           }
 
           foreach ($messages as $message) {
             $line = idx($message, 'line', 0);
 
             $this->inserts[] = qsprintf(
               $this->conn,
               '(%d, %s, %d, %s, %s, %s, %s)',
               $this->branch->getID(),
               $this->svnRoot.'/'.$path,
               $line,
               idx($message, 'code', ''),
               idx($message, 'severity', ''),
               idx($message, 'name', ''),
               idx($message, 'description', ''));
 
             if ($line && $this->needsBlame) {
               $this->blame[$path][$line] = true;
             }
           }
 
           if (count($this->deletes) >= 1024 || count($this->inserts) >= 256) {
             $this->saveLintMessages();
           }
         }
       }
 
     } catch (Exception $ex) {
       fprintf(STDERR, $ex->getMessage()."\n");
     }
   }
 
 
   private function saveLintMessages() {
     $this->conn->openTransaction();
 
     foreach (array_chunk($this->deletes, 1024) as $paths) {
       queryfx(
         $this->conn,
         'DELETE FROM %T WHERE branchID = %d AND path IN (%Ls)',
         PhabricatorRepository::TABLE_LINTMESSAGE,
         $this->branch->getID(),
         $paths);
     }
 
     foreach (array_chunk($this->inserts, 256) as $values) {
       queryfx(
         $this->conn,
         'INSERT INTO %T
           (branchID, path, line, code, severity, name, description)
           VALUES %Q',
         PhabricatorRepository::TABLE_LINTMESSAGE,
         implode(', ', $values));
     }
 
     $this->conn->saveTransaction();
 
     $this->deletes = array();
     $this->inserts = array();
   }
 
 
   private function blameAuthors() {
     $repository = id(new PhabricatorRepositoryQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withIDs(array($this->branch->getRepositoryID()))
       ->executeOne();
 
     $queries = array();
     $futures = array();
     foreach ($this->blame as $path => $lines) {
       $drequest = DiffusionRequest::newFromDictionary(array(
         'user' => PhabricatorUser::getOmnipotentUser(),
         'initFromConduit' => false,
         'repository' => $repository,
         'branch' => $this->branch->getName(),
         'path' => $path,
         'commit' => $this->lintCommit,
       ));
       $query = DiffusionFileContentQuery::newFromDiffusionRequest($drequest)
         ->setNeedsBlame(true);
       $queries[$path] = $query;
       $futures[$path] = $query->getFileContentFuture();
     }
 
     $authors = array();
 
-    foreach (Futures($futures)->limit(8) as $path => $future) {
+    $futures = id(new FutureIterator($futures))
+      ->limit(8);
+    foreach ($futures as $path => $future) {
       $queries[$path]->loadFileContentFromFuture($future);
       list(, $rev_list, $blame_dict) = $queries[$path]->getBlameData();
       foreach (array_keys($this->blame[$path]) as $line) {
         $commit_identifier = $rev_list[$line - 1];
         $author = idx($blame_dict[$commit_identifier], 'authorPHID');
         if ($author) {
           $authors[$author][$path][] = $line;
         }
       }
     }
 
     if ($authors) {
       $this->conn->openTransaction();
 
       foreach ($authors as $author => $paths) {
         $where = array();
         foreach ($paths as $path => $lines) {
           $where[] = qsprintf(
             $this->conn,
             '(path = %s AND line IN (%Ld))',
             $this->svnRoot.'/'.$path,
             $lines);
         }
         queryfx(
           $this->conn,
           'UPDATE %T SET authorPHID = %s WHERE %Q',
           PhabricatorRepository::TABLE_LINTMESSAGE,
           $author,
           implode(' OR ', $where));
       }
 
       $this->conn->saveTransaction();
     }
   }
 
 }
diff --git a/src/applications/diffusion/conduit/DiffusionDiffQueryConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionDiffQueryConduitAPIMethod.php
index c0b311c8eb..4dc2a2bac9 100644
--- a/src/applications/diffusion/conduit/DiffusionDiffQueryConduitAPIMethod.php
+++ b/src/applications/diffusion/conduit/DiffusionDiffQueryConduitAPIMethod.php
@@ -1,239 +1,239 @@
 <?php
 
 final class DiffusionDiffQueryConduitAPIMethod
   extends DiffusionQueryConduitAPIMethod {
 
   private $effectiveCommit;
 
   public function getAPIMethodName() {
     return 'diffusion.diffquery';
   }
 
   public function getMethodDescription() {
     return
       'Get diff information from a repository for a specific path at an '.
       '(optional) commit.';
   }
 
   public function defineReturnType() {
     return 'array';
   }
 
   protected function defineCustomParamTypes() {
     return array(
       'path' => 'required string',
       'commit' => 'optional string',
     );
   }
 
   protected function getResult(ConduitAPIRequest $request) {
     $result = parent::getResult($request);
 
     return array(
       'changes' => mpull($result, 'toDictionary'),
       'effectiveCommit' => $this->getEffectiveCommit($request),
     );
   }
 
   protected function getGitResult(ConduitAPIRequest $request) {
     return $this->getGitOrMercurialResult($request);
   }
 
   protected function getMercurialResult(ConduitAPIRequest $request) {
     return $this->getGitOrMercurialResult($request);
   }
 
   /**
    * NOTE: We have to work particularly hard for SVN as compared to other VCS.
    * That's okay but means this shares little code with the other VCS.
    */
   protected function getSVNResult(ConduitAPIRequest $request) {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $effective_commit = $this->getEffectiveCommit($request);
     if (!$effective_commit) {
       return $this->getEmptyResult();
     }
 
     $drequest = clone $drequest;
     $drequest->updateSymbolicCommit($effective_commit);
 
     $path_change_query = DiffusionPathChangeQuery::newFromDiffusionRequest(
       $drequest);
     $path_changes = $path_change_query->loadChanges();
 
     $path = null;
     foreach ($path_changes as $change) {
       if ($change->getPath() == $drequest->getPath()) {
         $path = $change;
       }
     }
 
     if (!$path) {
       return $this->getEmptyResult();
     }
 
     $change_type = $path->getChangeType();
     switch ($change_type) {
       case DifferentialChangeType::TYPE_MULTICOPY:
       case DifferentialChangeType::TYPE_DELETE:
         if ($path->getTargetPath()) {
           $old = array(
             $path->getTargetPath(),
             $path->getTargetCommitIdentifier(),
           );
         } else {
           $old = array($path->getPath(), $path->getCommitIdentifier() - 1);
         }
         $old_name = $path->getPath();
         $new_name = '';
         $new = null;
         break;
       case DifferentialChangeType::TYPE_ADD:
         $old = null;
         $new = array($path->getPath(), $path->getCommitIdentifier());
         $old_name = '';
         $new_name = $path->getPath();
         break;
       case DifferentialChangeType::TYPE_MOVE_HERE:
       case DifferentialChangeType::TYPE_COPY_HERE:
         $old = array(
           $path->getTargetPath(),
           $path->getTargetCommitIdentifier(),
         );
         $new = array($path->getPath(), $path->getCommitIdentifier());
         $old_name = $path->getTargetPath();
         $new_name = $path->getPath();
         break;
       case DifferentialChangeType::TYPE_MOVE_AWAY:
         $old = array(
           $path->getPath(),
           $path->getCommitIdentifier() - 1,
         );
         $old_name = $path->getPath();
         $new_name = null;
         $new = null;
         break;
       default:
         $old = array($path->getPath(), $path->getCommitIdentifier() - 1);
         $new = array($path->getPath(), $path->getCommitIdentifier());
         $old_name = $path->getPath();
         $new_name = $path->getPath();
         break;
     }
 
     $futures = array(
       'old' => $this->buildSVNContentFuture($old),
       'new' => $this->buildSVNContentFuture($new),
     );
     $futures = array_filter($futures);
 
-    foreach (Futures($futures) as $key => $future) {
+    foreach (new FutureIterator($futures) as $key => $future) {
       $stdout = '';
       try {
         list($stdout) = $future->resolvex();
       } catch (CommandException $e) {
         if ($path->getFileType() != DifferentialChangeType::FILE_DIRECTORY) {
           throw $e;
         }
       }
       $futures[$key] = $stdout;
     }
 
     $old_data = idx($futures, 'old', '');
     $new_data = idx($futures, 'new', '');
 
     $engine = new PhabricatorDifferenceEngine();
     $engine->setOldName($old_name);
     $engine->setNewName($new_name);
     $raw_diff = $engine->generateRawDiffFromFileContent($old_data, $new_data);
 
     $arcanist_changes = DiffusionPathChange::convertToArcanistChanges(
       $path_changes);
 
     $parser = $this->getDefaultParser();
     $parser->setChanges($arcanist_changes);
     $parser->forcePath($path->getPath());
     $changes = $parser->parseDiff($raw_diff);
 
     $change = $changes[$path->getPath()];
 
     return array($change);
   }
 
   private function getEffectiveCommit(ConduitAPIRequest $request) {
     if ($this->effectiveCommit === null) {
       $drequest = $this->getDiffusionRequest();
 
       $path = $drequest->getPath();
       $result = DiffusionQuery::callConduitWithDiffusionRequest(
         $request->getUser(),
         $drequest,
         'diffusion.lastmodifiedquery',
         array(
           'paths' => array($path => $drequest->getStableCommit()),
         ));
 
       $this->effectiveCommit = idx($result, $path);
     }
 
     return $this->effectiveCommit;
   }
 
   private function buildSVNContentFuture($spec) {
     if (!$spec) {
       return null;
     }
 
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     list($ref, $rev) = $spec;
     return $repository->getRemoteCommandFuture(
       'cat %s',
       $repository->getSubversionPathURI($ref, $rev));
   }
 
   private function getGitOrMercurialResult(ConduitAPIRequest $request) {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $effective_commit = $this->getEffectiveCommit($request);
     if (!$effective_commit) {
       return $this->getEmptyResult(1);
     }
 
     $raw_query = DiffusionRawDiffQuery::newFromDiffusionRequest($drequest)
       ->setAnchorCommit($effective_commit);
 
     $raw_diff = $raw_query->loadRawDiff();
     if (!$raw_diff) {
       return $this->getEmptyResult(2);
     }
 
     $parser = $this->getDefaultParser();
     $changes = $parser->parseDiff($raw_diff);
 
     return $changes;
   }
 
   private function getDefaultParser() {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $parser = new ArcanistDiffParser();
     $try_encoding = $repository->getDetail('encoding');
     if ($try_encoding) {
       $parser->setTryEncoding($try_encoding);
     }
     $parser->setDetectBinaryFiles(true);
 
     return $parser;
   }
 
   private function getEmptyResult() {
     return array();
   }
 
 }
diff --git a/src/applications/diffusion/conduit/DiffusionTagsQueryConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionTagsQueryConduitAPIMethod.php
index 4f8d6a959f..1ece4dd85b 100644
--- a/src/applications/diffusion/conduit/DiffusionTagsQueryConduitAPIMethod.php
+++ b/src/applications/diffusion/conduit/DiffusionTagsQueryConduitAPIMethod.php
@@ -1,167 +1,168 @@
 <?php
 
 final class DiffusionTagsQueryConduitAPIMethod
   extends DiffusionQueryConduitAPIMethod {
 
   public function getAPIMethodName() {
     return 'diffusion.tagsquery';
   }
 
   public function getMethodDescription() {
     return pht('Retrieve information about tags in a repository.');
   }
 
   public function defineReturnType() {
     return 'array';
   }
 
   protected function defineCustomParamTypes() {
     return array(
       'names' => 'optional list<string>',
       'commit' => 'optional string',
       'needMessages' => 'optional bool',
       'offset' => 'optional int',
       'limit' => 'optional int',
     );
   }
 
   protected function getGitResult(ConduitAPIRequest $request) {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
     $commit = $drequest->getSymbolicCommit();
 
     $commit_filter = null;
     if ($commit) {
       $commit_filter = $this->loadTagNamesForCommit($commit);
     }
 
     $name_filter = $request->getValue('names', null);
 
     $all_tags = $this->loadGitTagList();
     $all_tags = mpull($all_tags, null, 'getName');
 
     if ($name_filter !== null) {
       $all_tags = array_intersect_key($all_tags, array_fuse($name_filter));
     }
     if ($commit_filter !== null) {
       $all_tags = array_intersect_key($all_tags, $commit_filter);
     }
 
     $tags = array_values($all_tags);
 
     $offset = $request->getValue('offset');
     $limit = $request->getValue('limit');
     if ($offset) {
       $tags = array_slice($tags, $offset);
     }
 
     if ($limit) {
       $tags = array_slice($tags, 0, $limit);
     }
 
     if ($request->getValue('needMessages')) {
       $this->loadMessagesForTags($all_tags);
     }
 
     return mpull($tags, 'toDictionary');
   }
 
   private function loadGitTagList() {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $refs = id(new DiffusionLowLevelGitRefQuery())
       ->setRepository($repository)
       ->withIsTag(true)
       ->execute();
 
     $tags = array();
     foreach ($refs as $ref) {
       $fields = $ref->getRawFields();
       $tag = id(new DiffusionRepositoryTag())
         ->setAuthor($fields['author'])
         ->setEpoch($fields['epoch'])
         ->setCommitIdentifier($ref->getCommitIdentifier())
         ->setName($ref->getShortName())
         ->setDescription($fields['subject'])
         ->setType('git/'.$fields['objecttype']);
 
       $tags[] = $tag;
     }
 
     return $tags;
   }
 
   private function loadTagNamesForCommit($commit) {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     list($err, $stdout) = $repository->execLocalCommand(
       'tag -l --contains %s',
       $commit);
 
     if ($err) {
       // Git exits with an error code if the commit is bogus.
       return array();
     }
 
     $stdout = rtrim($stdout, "\n");
     if (!strlen($stdout)) {
       return array();
     }
 
     $tag_names = explode("\n", $stdout);
     $tag_names = array_fill_keys($tag_names, true);
 
     return $tag_names;
   }
 
   private function loadMessagesForTags(array $tags) {
     assert_instances_of($tags, 'DiffusionRepositoryTag');
 
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
 
     $futures = array();
     foreach ($tags as $key => $tag) {
       $futures[$key] = $repository->getLocalCommandFuture(
         'cat-file tag %s',
         $tag->getName());
     }
 
-    Futures($futures)->resolveAll();
+    id(new FutureIterator($futures))
+      ->resolveAll();
 
     foreach ($tags as $key => $tag) {
       $future = $futures[$key];
       list($err, $stdout) = $future->resolve();
 
       $message = null;
       if ($err) {
         // Not all tags are actually "tag" objects: a "tag" object is only
         // created if you provide a message or sign the tag. Tags created with
         // `git tag x [commit]` are "lightweight tags" and `git cat-file tag`
         // will fail on them. This is fine: they don't have messages.
       } else {
         $parts = explode("\n\n", $stdout, 2);
         if (count($parts) == 2) {
           $message = last($parts);
         }
       }
 
       $tag->attachMessage($message);
     }
 
     return $tags;
   }
 
   protected function getMercurialResult(ConduitAPIRequest $request) {
     // For now, we don't support Mercurial tags via API.
     return array();
   }
 
   protected function getSVNResult(ConduitAPIRequest $request) {
     // Subversion has no meaningful concept of tags.
     return array();
   }
 
 }
diff --git a/src/applications/diffusion/controller/DiffusionBrowseSearchController.php b/src/applications/diffusion/controller/DiffusionBrowseSearchController.php
index 16bb1bc761..8b6f91c38e 100644
--- a/src/applications/diffusion/controller/DiffusionBrowseSearchController.php
+++ b/src/applications/diffusion/controller/DiffusionBrowseSearchController.php
@@ -1,206 +1,208 @@
 <?php
 
 final class DiffusionBrowseSearchController extends DiffusionBrowseController {
 
   public function processRequest() {
     $drequest = $this->diffusionRequest;
 
     $actions = $this->buildActionView($drequest);
     $properties = $this->buildPropertyView($drequest, $actions);
 
     $object_box = id(new PHUIObjectBoxView())
       ->setHeader($this->buildHeaderView($drequest))
       ->addPropertyList($properties);
 
     $content = array();
 
     $content[] = $object_box;
     $content[] = $this->renderSearchForm($collapsed = false);
     $content[] = $this->renderSearchResults();
 
     $crumbs = $this->buildCrumbs(
       array(
         'branch' => true,
         'path'   => true,
         'view'   => 'browse',
       ));
 
     return $this->buildApplicationPage(
       array(
         $crumbs,
         $content,
       ),
       array(
         'title' => array(
           nonempty(basename($drequest->getPath()), '/'),
           $drequest->getRepository()->getCallsign().' Repository',
         ),
       ));
   }
 
   private function renderSearchResults() {
     $drequest = $this->getDiffusionRequest();
     $repository = $drequest->getRepository();
     $results = array();
 
     $limit = 100;
     $page = $this->getRequest()->getInt('page', 0);
     $pager = new AphrontPagerView();
     $pager->setPageSize($limit);
     $pager->setOffset($page);
     $pager->setURI($this->getRequest()->getRequestURI(), 'page');
 
     $search_mode = null;
 
     try {
       if (strlen($this->getRequest()->getStr('grep'))) {
         $search_mode = 'grep';
         $query_string = $this->getRequest()->getStr('grep');
         $results = $this->callConduitWithDiffusionRequest(
           'diffusion.searchquery',
           array(
             'grep' => $query_string,
             'commit' => $drequest->getStableCommit(),
             'path' => $drequest->getPath(),
             'limit' => $limit + 1,
             'offset' => $page,
           ));
       } else { // Filename search.
         $search_mode = 'find';
         $query_string = $this->getRequest()->getStr('find');
         $results = $this->callConduitWithDiffusionRequest(
           'diffusion.querypaths',
           array(
             'pattern' => $query_string,
             'commit' => $drequest->getStableCommit(),
             'path' => $drequest->getPath(),
             'limit' => $limit + 1,
             'offset' => $page,
           ));
       }
     } catch (ConduitException $ex) {
       $err = $ex->getErrorDescription();
       if ($err != '') {
         return id(new AphrontErrorView())
           ->setTitle(pht('Search Error'))
           ->appendChild($err);
       }
     }
 
     $results = $pager->sliceResults($results);
 
     if ($search_mode == 'grep') {
       $table = $this->renderGrepResults($results);
       $header = pht(
         'File content matching "%s" under "%s"',
         $query_string,
         nonempty($drequest->getPath(), '/'));
     } else {
       $table = $this->renderFindResults($results);
       $header = pht(
         'Paths matching "%s" under "%s"',
         $query_string,
         nonempty($drequest->getPath(), '/'));
     }
 
     $box = id(new PHUIObjectBoxView())
       ->setHeaderText($header)
       ->appendChild($table);
 
     $pager_box = id(new PHUIBoxView())
       ->addMargin(PHUI::MARGIN_LARGE)
       ->appendChild($pager);
 
     return array($box, $pager_box);
   }
 
   private function renderGrepResults(array $results) {
     $drequest = $this->getDiffusionRequest();
 
     require_celerity_resource('syntax-highlighting-css');
 
     // NOTE: This can be wrong because we may find the string inside the
     // comment. But it's correct in most cases and highlighting the whole file
     // would be too expensive.
     $futures = array();
     $engine = PhabricatorSyntaxHighlighter::newEngine();
     foreach ($results as $result) {
       list($path, $line, $string) = $result;
       $futures["{$path}:{$line}"] = $engine->getHighlightFuture(
         $engine->getLanguageFromFilename($path),
         ltrim($string));
     }
 
     try {
-      Futures($futures)->limit(8)->resolveAll();
+      id(new FutureIterator($futures))
+        ->limit(8)
+        ->resolveAll();
     } catch (PhutilSyntaxHighlighterException $ex) {}
 
     $rows = array();
     foreach ($results as $result) {
       list($path, $line, $string) = $result;
 
       $href = $drequest->generateURI(array(
         'action' => 'browse',
         'path' => $path,
         'line' => $line,
       ));
 
       try {
         $string = $futures["{$path}:{$line}"]->resolve();
       } catch (PhutilSyntaxHighlighterException $ex) {}
 
       $string = phutil_tag(
         'pre',
         array('class' => 'PhabricatorMonospaced'),
         $string);
 
       $path = Filesystem::readablePath($path, $drequest->getPath());
 
       $rows[] = array(
         phutil_tag('a', array('href' => $href), $path),
         $line,
         $string,
       );
     }
 
     $table = id(new AphrontTableView($rows))
       ->setClassName('remarkup-code')
       ->setHeaders(array(pht('Path'), pht('Line'), pht('String')))
       ->setColumnClasses(array('', 'n', 'wide'))
       ->setNoDataString(
         pht(
           'The pattern you searched for was not found in the content of any '.
           'files.'));
 
     return $table;
   }
 
   private function renderFindResults(array $results) {
     $drequest = $this->getDiffusionRequest();
 
     $rows = array();
     foreach ($results as $result) {
       $href = $drequest->generateURI(array(
         'action' => 'browse',
         'path' => $result,
       ));
 
       $readable = Filesystem::readablePath($result, $drequest->getPath());
 
       $rows[] = array(
         phutil_tag('a', array('href' => $href), $readable),
       );
     }
 
     $table = id(new AphrontTableView($rows))
       ->setHeaders(array(pht('Path')))
       ->setColumnClasses(array('wide'))
       ->setNoDataString(
         pht(
           'The pattern you searched for did not match the names of any '.
           'files.'));
 
     return $table;
   }
 
 }
diff --git a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
index c4d509fdb8..080a69c306 100644
--- a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
+++ b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
@@ -1,1189 +1,1193 @@
 <?php
 
 /**
  * @task config   Configuring the Hook Engine
  * @task hook     Hook Execution
  * @task git      Git Hooks
  * @task hg       Mercurial Hooks
  * @task svn      Subversion Hooks
  * @task internal Internals
  */
 final class DiffusionCommitHookEngine extends Phobject {
 
   const ENV_USER = 'PHABRICATOR_USER';
   const ENV_REMOTE_ADDRESS = 'PHABRICATOR_REMOTE_ADDRESS';
   const ENV_REMOTE_PROTOCOL = 'PHABRICATOR_REMOTE_PROTOCOL';
 
   const EMPTY_HASH = '0000000000000000000000000000000000000000';
 
   private $viewer;
   private $repository;
   private $stdin;
   private $originalArgv;
   private $subversionTransaction;
   private $subversionRepository;
   private $remoteAddress;
   private $remoteProtocol;
   private $transactionKey;
   private $mercurialHook;
   private $mercurialCommits = array();
   private $gitCommits = array();
 
   private $heraldViewerProjects;
   private $rejectCode = PhabricatorRepositoryPushLog::REJECT_BROKEN;
   private $rejectDetails;
   private $emailPHIDs = array();
 
 
 /* -(  Config  )------------------------------------------------------------- */
 
 
   public function setRemoteProtocol($remote_protocol) {
     $this->remoteProtocol = $remote_protocol;
     return $this;
   }
 
   public function getRemoteProtocol() {
     return $this->remoteProtocol;
   }
 
   public function setRemoteAddress($remote_address) {
     $this->remoteAddress = $remote_address;
     return $this;
   }
 
   public function getRemoteAddress() {
     return $this->remoteAddress;
   }
 
   private function getRemoteAddressForLog() {
     // If whatever we have here isn't a valid IPv4 address, just store `null`.
     // Older versions of PHP return `-1` on failure instead of `false`.
     $remote_address = $this->getRemoteAddress();
     $remote_address = max(0, ip2long($remote_address));
     $remote_address = nonempty($remote_address, null);
     return $remote_address;
   }
 
   public function setSubversionTransactionInfo($transaction, $repository) {
     $this->subversionTransaction = $transaction;
     $this->subversionRepository = $repository;
     return $this;
   }
 
   public function setStdin($stdin) {
     $this->stdin = $stdin;
     return $this;
   }
 
   public function getStdin() {
     return $this->stdin;
   }
 
   public function setOriginalArgv(array $original_argv) {
     $this->originalArgv = $original_argv;
     return $this;
   }
 
   public function getOriginalArgv() {
     return $this->originalArgv;
   }
 
   public function setRepository(PhabricatorRepository $repository) {
     $this->repository = $repository;
     return $this;
   }
 
   public function getRepository() {
     return $this->repository;
   }
 
   public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
     return $this;
   }
 
   public function getViewer() {
     return $this->viewer;
   }
 
   public function setMercurialHook($mercurial_hook) {
     $this->mercurialHook = $mercurial_hook;
     return $this;
   }
 
   public function getMercurialHook() {
     return $this->mercurialHook;
   }
 
 
 /* -(  Hook Execution  )----------------------------------------------------- */
 
 
   public function execute() {
     $ref_updates = $this->findRefUpdates();
     $all_updates = $ref_updates;
 
     $caught = null;
     try {
 
       try {
         $this->rejectDangerousChanges($ref_updates);
       } catch (DiffusionCommitHookRejectException $ex) {
         // If we're rejecting dangerous changes, flag everything that we've
         // seen as rejected so it's clear that none of it was accepted.
         $this->rejectCode = PhabricatorRepositoryPushLog::REJECT_DANGEROUS;
         throw $ex;
       }
 
       $this->applyHeraldRefRules($ref_updates, $all_updates);
 
       $content_updates = $this->findContentUpdates($ref_updates);
       $all_updates = array_merge($all_updates, $content_updates);
 
       $this->applyHeraldContentRules($content_updates, $all_updates);
 
       // Run custom scripts in `hook.d/` directories.
       $this->applyCustomHooks($all_updates);
 
       // If we make it this far, we're accepting these changes. Mark all the
       // logs as accepted.
       $this->rejectCode = PhabricatorRepositoryPushLog::REJECT_ACCEPT;
     } catch (Exception $ex) {
       // We'll throw this again in a minute, but we want to save all the logs
       // first.
       $caught = $ex;
     }
 
     // Save all the logs no matter what the outcome was.
     $event = $this->newPushEvent();
 
     $event->setRejectCode($this->rejectCode);
     $event->setRejectDetails($this->rejectDetails);
 
     $event->openTransaction();
       $event->save();
       foreach ($all_updates as $update) {
         $update->setPushEventPHID($event->getPHID());
         $update->save();
       }
     $event->saveTransaction();
 
     if ($caught) {
       throw $caught;
     }
 
     if ($this->emailPHIDs) {
       // If Herald rules triggered email to users, queue a worker to send the
       // mail. We do this out-of-process so that we block pushes as briefly
       // as possible.
 
       // (We do need to pull some commit info here because the commit objects
       // may not exist yet when this worker runs, which could be immediately.)
 
       PhabricatorWorker::scheduleTask(
         'PhabricatorRepositoryPushMailWorker',
         array(
           'eventPHID' => $event->getPHID(),
           'emailPHIDs' => array_values($this->emailPHIDs),
           'info' => $this->loadCommitInfoForWorker($all_updates),
         ),
         array(
           'priority' => PhabricatorWorker::PRIORITY_ALERTS,
         ));
     }
 
     return 0;
   }
 
   private function findRefUpdates() {
     $type = $this->getRepository()->getVersionControlSystem();
     switch ($type) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         return $this->findGitRefUpdates();
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return $this->findMercurialRefUpdates();
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         return $this->findSubversionRefUpdates();
       default:
         throw new Exception(pht('Unsupported repository type "%s"!', $type));
     }
   }
 
   private function rejectDangerousChanges(array $ref_updates) {
     assert_instances_of($ref_updates, 'PhabricatorRepositoryPushLog');
 
     $repository = $this->getRepository();
     if ($repository->shouldAllowDangerousChanges()) {
       return;
     }
 
     $flag_dangerous = PhabricatorRepositoryPushLog::CHANGEFLAG_DANGEROUS;
 
     foreach ($ref_updates as $ref_update) {
       if (!$ref_update->hasChangeFlags($flag_dangerous)) {
         // This is not a dangerous change.
         continue;
       }
 
       // We either have a branch deletion or a non fast-forward branch update.
       // Format a message and reject the push.
 
       $message = pht(
         "DANGEROUS CHANGE: %s\n".
         "Dangerous change protection is enabled for this repository.\n".
         "Edit the repository configuration before making dangerous changes.",
         $ref_update->getDangerousChangeDescription());
 
       throw new DiffusionCommitHookRejectException($message);
     }
   }
 
   private function findContentUpdates(array $ref_updates) {
     assert_instances_of($ref_updates, 'PhabricatorRepositoryPushLog');
 
     $type = $this->getRepository()->getVersionControlSystem();
     switch ($type) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         return $this->findGitContentUpdates($ref_updates);
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return $this->findMercurialContentUpdates($ref_updates);
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         return $this->findSubversionContentUpdates($ref_updates);
       default:
         throw new Exception(pht('Unsupported repository type "%s"!', $type));
     }
   }
 
 
 /* -(  Herald  )------------------------------------------------------------- */
 
   private function applyHeraldRefRules(
     array $ref_updates,
     array $all_updates) {
     $this->applyHeraldRules(
       $ref_updates,
       new HeraldPreCommitRefAdapter(),
       $all_updates);
   }
 
   private function applyHeraldContentRules(
     array $content_updates,
     array $all_updates) {
     $this->applyHeraldRules(
       $content_updates,
       new HeraldPreCommitContentAdapter(),
       $all_updates);
   }
 
   private function applyHeraldRules(
     array $updates,
     HeraldAdapter $adapter_template,
     array $all_updates) {
 
     if (!$updates) {
       return;
     }
 
     $adapter_template->setHookEngine($this);
 
     $engine = new HeraldEngine();
     $rules = null;
     $blocking_effect = null;
     $blocked_update = null;
     foreach ($updates as $update) {
       $adapter = id(clone $adapter_template)
         ->setPushLog($update);
 
       if ($rules === null) {
         $rules = $engine->loadRulesForAdapter($adapter);
       }
 
       $effects = $engine->applyRules($rules, $adapter);
       $engine->applyEffects($effects, $adapter, $rules);
       $xscript = $engine->getTranscript();
 
       // Store any PHIDs we want to send email to for later.
       foreach ($adapter->getEmailPHIDs() as $email_phid) {
         $this->emailPHIDs[$email_phid] = $email_phid;
       }
 
       if ($blocking_effect === null) {
         foreach ($effects as $effect) {
           if ($effect->getAction() == HeraldAdapter::ACTION_BLOCK) {
             $blocking_effect = $effect;
             $blocked_update = $update;
             break;
           }
         }
       }
     }
 
     if ($blocking_effect) {
       $this->rejectCode = PhabricatorRepositoryPushLog::REJECT_HERALD;
       $this->rejectDetails = $blocking_effect->getRulePHID();
 
       $message = $blocking_effect->getTarget();
       if (!strlen($message)) {
         $message = pht('(None.)');
       }
 
       $rules = mpull($rules, null, 'getID');
       $rule = idx($rules, $effect->getRuleID());
       if ($rule && strlen($rule->getName())) {
         $rule_name = $rule->getName();
       } else {
         $rule_name = pht('Unnamed Herald Rule');
       }
 
       $blocked_ref_name = coalesce(
         $blocked_update->getRefName(),
         $blocked_update->getRefNewShort());
       $blocked_name = $blocked_update->getRefType().'/'.$blocked_ref_name;
 
       throw new DiffusionCommitHookRejectException(
         pht(
           "This push was rejected by Herald push rule %s.\n".
           "Change: %s\n".
           "  Rule: %s\n".
           "Reason: %s",
           'H'.$blocking_effect->getRuleID(),
           $blocked_name,
           $rule_name,
           $message));
     }
   }
 
   public function loadViewerProjectPHIDsForHerald() {
     // This just caches the viewer's projects so we don't need to load them
     // over and over again when applying Herald rules.
     if ($this->heraldViewerProjects === null) {
       $this->heraldViewerProjects = id(new PhabricatorProjectQuery())
         ->setViewer($this->getViewer())
         ->withMemberPHIDs(array($this->getViewer()->getPHID()))
         ->execute();
     }
 
     return mpull($this->heraldViewerProjects, 'getPHID');
   }
 
 
 /* -(  Git  )---------------------------------------------------------------- */
 
 
   private function findGitRefUpdates() {
     $ref_updates = array();
 
     // First, parse stdin, which lists all the ref changes. The input looks
     // like this:
     //
     //   <old hash> <new hash> <ref>
 
     $stdin = $this->getStdin();
     $lines = phutil_split_lines($stdin, $retain_endings = false);
     foreach ($lines as $line) {
       $parts = explode(' ', $line, 3);
       if (count($parts) != 3) {
         throw new Exception(pht('Expected "old new ref", got "%s".', $line));
       }
 
       $ref_old = $parts[0];
       $ref_new = $parts[1];
       $ref_raw = $parts[2];
 
       if (preg_match('(^refs/heads/)', $ref_raw)) {
         $ref_type = PhabricatorRepositoryPushLog::REFTYPE_BRANCH;
         $ref_raw = substr($ref_raw, strlen('refs/heads/'));
       } else if (preg_match('(^refs/tags/)', $ref_raw)) {
         $ref_type = PhabricatorRepositoryPushLog::REFTYPE_TAG;
         $ref_raw = substr($ref_raw, strlen('refs/tags/'));
       } else {
         throw new Exception(
           pht(
             "Unable to identify the reftype of '%s'. Rejecting push.",
             $ref_raw));
       }
 
       $ref_update = $this->newPushLog()
         ->setRefType($ref_type)
         ->setRefName($ref_raw)
         ->setRefOld($ref_old)
         ->setRefNew($ref_new);
 
       $ref_updates[] = $ref_update;
     }
 
     $this->findGitMergeBases($ref_updates);
     $this->findGitChangeFlags($ref_updates);
 
     return $ref_updates;
   }
 
 
   private function findGitMergeBases(array $ref_updates) {
     assert_instances_of($ref_updates, 'PhabricatorRepositoryPushLog');
 
     $futures = array();
     foreach ($ref_updates as $key => $ref_update) {
       // If the old hash is "00000...", the ref is being created (either a new
       // branch, or a new tag). If the new hash is "00000...", the ref is being
       // deleted. If both are nonempty, the ref is being updated. For updates,
       // we'll figure out the `merge-base` of the old and new objects here. This
       // lets us reject non-FF changes cheaply; later, we'll figure out exactly
       // which commits are new.
       $ref_old = $ref_update->getRefOld();
       $ref_new = $ref_update->getRefNew();
 
       if (($ref_old === self::EMPTY_HASH) ||
           ($ref_new === self::EMPTY_HASH)) {
         continue;
       }
 
       $futures[$key] = $this->getRepository()->getLocalCommandFuture(
         'merge-base %s %s',
         $ref_old,
         $ref_new);
     }
 
-    foreach (Futures($futures)->limit(8) as $key => $future) {
+    $futures = id(new FutureIterator($futures))
+      ->limit(8);
+    foreach ($futures as $key => $future) {
 
       // If 'old' and 'new' have no common ancestors (for example, a force push
       // which completely rewrites a ref), `git merge-base` will exit with
       // an error and no output. It would be nice to find a positive test
       // for this instead, but I couldn't immediately come up with one. See
       // T4224. Assume this means there are no ancestors.
 
       list($err, $stdout) = $future->resolve();
 
       if ($err) {
         $merge_base = null;
       } else {
         $merge_base = rtrim($stdout, "\n");
       }
 
       $ref_update = $ref_updates[$key];
       $ref_update->setMergeBase($merge_base);
     }
 
     return $ref_updates;
   }
 
 
   private function findGitChangeFlags(array $ref_updates) {
     assert_instances_of($ref_updates, 'PhabricatorRepositoryPushLog');
 
     foreach ($ref_updates as $key => $ref_update) {
       $ref_old = $ref_update->getRefOld();
       $ref_new = $ref_update->getRefNew();
       $ref_type = $ref_update->getRefType();
 
       $ref_flags = 0;
       $dangerous = null;
 
       if (($ref_old === self::EMPTY_HASH) && ($ref_new === self::EMPTY_HASH)) {
         // This happens if you try to delete a tag or branch which does not
         // exist by pushing directly to the ref. Git will warn about it but
         // allow it. Just call it a delete, without flagging it as dangerous.
         $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
       } else if ($ref_old === self::EMPTY_HASH) {
         $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_ADD;
       } else if ($ref_new === self::EMPTY_HASH) {
         $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
         if ($ref_type == PhabricatorRepositoryPushLog::REFTYPE_BRANCH) {
           $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DANGEROUS;
           $dangerous = pht(
             "The change you're attempting to push deletes the branch '%s'.",
             $ref_update->getRefName());
         }
       } else {
         $merge_base = $ref_update->getMergeBase();
         if ($merge_base == $ref_old) {
           // This is a fast-forward update to an existing branch.
           // These are safe.
           $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_APPEND;
         } else {
           $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_REWRITE;
 
           // For now, we don't consider deleting or moving tags to be a
           // "dangerous" update. It's way harder to get wrong and should be easy
           // to recover from once we have better logging. Only add the dangerous
           // flag if this ref is a branch.
 
           if ($ref_type == PhabricatorRepositoryPushLog::REFTYPE_BRANCH) {
             $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DANGEROUS;
 
             $dangerous = pht(
               "The change you're attempting to push updates the branch '%s' ".
               "from '%s' to '%s', but this is not a fast-forward. Pushes ".
               "which rewrite published branch history are dangerous.",
               $ref_update->getRefName(),
               $ref_update->getRefOldShort(),
               $ref_update->getRefNewShort());
           }
         }
       }
 
       $ref_update->setChangeFlags($ref_flags);
       if ($dangerous !== null) {
         $ref_update->attachDangerousChangeDescription($dangerous);
       }
     }
 
     return $ref_updates;
   }
 
 
   private function findGitContentUpdates(array $ref_updates) {
     $flag_delete = PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
 
     $futures = array();
     foreach ($ref_updates as $key => $ref_update) {
       if ($ref_update->hasChangeFlags($flag_delete)) {
         // Deleting a branch or tag can never create any new commits.
         continue;
       }
 
       // NOTE: This piece of magic finds all new commits, by walking backward
       // from the new value to the value of *any* existing ref in the
       // repository. Particularly, this will cover the cases of a new branch, a
       // completely moved tag, etc.
       $futures[$key] = $this->getRepository()->getLocalCommandFuture(
         'log --format=%s %s --not --all',
         '%H',
         $ref_update->getRefNew());
     }
 
     $content_updates = array();
-    foreach (Futures($futures)->limit(8) as $key => $future) {
+    $futures = id(new FutureIterator($futures))
+      ->limit(8);
+    foreach ($futures as $key => $future) {
       list($stdout) = $future->resolvex();
 
       if (!strlen(trim($stdout))) {
         // This change doesn't have any new commits. One common case of this
         // is creating a new tag which points at an existing commit.
         continue;
       }
 
       $commits = phutil_split_lines($stdout, $retain_newlines = false);
 
       // If we're looking at a branch, mark all of the new commits as on that
       // branch. It's only possible for these commits to be on updated branches,
       // since any other branch heads are necessarily behind them.
       $branch_name = null;
       $ref_update = $ref_updates[$key];
       $type_branch = PhabricatorRepositoryPushLog::REFTYPE_BRANCH;
       if ($ref_update->getRefType() == $type_branch) {
         $branch_name = $ref_update->getRefName();
       }
 
       foreach ($commits as $commit) {
         if ($branch_name) {
           $this->gitCommits[$commit][] = $branch_name;
         }
         $content_updates[$commit] = $this->newPushLog()
           ->setRefType(PhabricatorRepositoryPushLog::REFTYPE_COMMIT)
           ->setRefNew($commit)
           ->setChangeFlags(PhabricatorRepositoryPushLog::CHANGEFLAG_ADD);
       }
     }
 
     return $content_updates;
   }
 
 /* -(  Custom  )------------------------------------------------------------- */
 
   private function applyCustomHooks(array $updates) {
     $args = $this->getOriginalArgv();
     $stdin = $this->getStdin();
     $console = PhutilConsole::getConsole();
 
     $env = array(
       'PHABRICATOR_REPOSITORY' => $this->getRepository()->getCallsign(),
       self::ENV_USER => $this->getViewer()->getUsername(),
       self::ENV_REMOTE_PROTOCOL => $this->getRemoteProtocol(),
       self::ENV_REMOTE_ADDRESS => $this->getRemoteAddress(),
     );
 
     $directories = $this->getRepository()->getHookDirectories();
     foreach ($directories as $directory) {
       $hooks = $this->getExecutablesInDirectory($directory);
       sort($hooks);
       foreach ($hooks as $hook) {
         // NOTE: We're explicitly running the hooks in sequential order to
         // make this more predictable.
         $future = id(new ExecFuture('%s %Ls', $hook, $args))
           ->setEnv($env, $wipe_process_env = false)
           ->write($stdin);
 
         list($err, $stdout, $stderr) = $future->resolve();
         if (!$err) {
           // This hook ran OK, but echo its output in case there was something
           // informative.
           $console->writeOut('%s', $stdout);
           $console->writeErr('%s', $stderr);
           continue;
         }
 
         $this->rejectCode = PhabricatorRepositoryPushLog::REJECT_EXTERNAL;
         $this->rejectDetails = basename($hook);
 
         throw new DiffusionCommitHookRejectException(
           pht(
             "This push was rejected by custom hook script '%s':\n\n%s%s",
             basename($hook),
             $stdout,
             $stderr));
       }
     }
   }
 
   private function getExecutablesInDirectory($directory) {
     $executables = array();
 
     if (!Filesystem::pathExists($directory)) {
       return $executables;
     }
 
     foreach (Filesystem::listDirectory($directory) as $path) {
       $full_path = $directory.DIRECTORY_SEPARATOR.$path;
       if (!is_executable($full_path)) {
         // Don't include non-executable files.
         continue;
       }
 
       if (basename($full_path) == 'README') {
         // Don't include README, even if it is marked as executable. It almost
         // certainly got caught in the crossfire of a sweeping `chmod`, since
         // users do this with some frequency.
         continue;
       }
 
       $executables[] = $full_path;
     }
 
     return $executables;
   }
 
 
 /* -(  Mercurial  )---------------------------------------------------------- */
 
 
   private function findMercurialRefUpdates() {
     $hook = $this->getMercurialHook();
     switch ($hook) {
       case 'pretxnchangegroup':
         return $this->findMercurialChangegroupRefUpdates();
       case 'prepushkey':
         return $this->findMercurialPushKeyRefUpdates();
       default:
         throw new Exception(pht('Unrecognized hook "%s"!', $hook));
     }
   }
 
   private function findMercurialChangegroupRefUpdates() {
     $hg_node = getenv('HG_NODE');
     if (!$hg_node) {
       throw new Exception(pht('Expected HG_NODE in environment!'));
     }
 
     // NOTE: We need to make sure this is passed to subprocesses, or they won't
     // be able to see new commits. Mercurial uses this as a marker to determine
     // whether the pending changes are visible or not.
     $_ENV['HG_PENDING'] = getenv('HG_PENDING');
     $repository = $this->getRepository();
 
     $futures = array();
 
     foreach (array('old', 'new') as $key) {
       $futures[$key] = $repository->getLocalCommandFuture(
         'heads --template %s',
         '{node}\1{branch}\2');
     }
     // Wipe HG_PENDING out of the old environment so we see the pre-commit
     // state of the repository.
     $futures['old']->updateEnv('HG_PENDING', null);
 
     $futures['commits'] = $repository->getLocalCommandFuture(
       'log --rev %s --template %s',
       hgsprintf('%s:%s', $hg_node, 'tip'),
       '{node}\1{branch}\2');
 
     // Resolve all of the futures now. We don't need the 'commits' future yet,
     // but it simplifies the logic to just get it out of the way.
-    foreach (Futures($futures) as $future) {
+    foreach (new FutureIterator($futures) as $future) {
       $future->resolve();
     }
 
     list($commit_raw) = $futures['commits']->resolvex();
     $commit_map = $this->parseMercurialCommits($commit_raw);
     $this->mercurialCommits = $commit_map;
 
     // NOTE: `hg heads` exits with an error code and no output if the repository
     // has no heads. Most commonly this happens on a new repository. We know
     // we can run `hg` successfully since the `hg log` above didn't error, so
     // just ignore the error code.
 
     list($err, $old_raw) = $futures['old']->resolve();
     $old_refs = $this->parseMercurialHeads($old_raw);
 
     list($err, $new_raw) = $futures['new']->resolve();
     $new_refs = $this->parseMercurialHeads($new_raw);
 
     $all_refs = array_keys($old_refs + $new_refs);
 
     $ref_updates = array();
     foreach ($all_refs as $ref) {
       $old_heads = idx($old_refs, $ref, array());
       $new_heads = idx($new_refs, $ref, array());
 
       sort($old_heads);
       sort($new_heads);
 
       if (!$old_heads && !$new_heads) {
         // This should never be possible, as it makes no sense. Explode.
         throw new Exception(
           pht(
             'Mercurial repository has no new or old heads for branch "%s" '.
             'after push. This makes no sense; rejecting change.',
             $ref));
       }
 
       if ($old_heads === $new_heads) {
         // No changes to this branch, so skip it.
         continue;
       }
 
       $stray_heads = array();
 
       if ($old_heads && !$new_heads) {
         // This is a branch deletion with "--close-branch".
         $head_map = array();
         foreach ($old_heads as $old_head) {
           $head_map[$old_head] = array(self::EMPTY_HASH);
         }
       } else if (count($old_heads) > 1) {
         // HORRIBLE: In Mercurial, branches can have multiple heads. If the
         // old branch had multiple heads, we need to figure out which new
         // heads descend from which old heads, so we can tell whether you're
         // actively creating new heads (dangerous) or just working in a
         // repository that's already full of garbage (strongly discouraged but
         // not as inherently dangerous). These cases should be very uncommon.
 
         // NOTE: We're only looking for heads on the same branch. The old
         // tip of the branch may be the branchpoint for other branches, but that
         // is OK.
 
         $dfutures = array();
         foreach ($old_heads as $old_head) {
           $dfutures[$old_head] = $repository->getLocalCommandFuture(
             'log --branch %s --rev %s --template %s',
             $ref,
             hgsprintf('(descendants(%s) and head())', $old_head),
             '{node}\1');
         }
 
         $head_map = array();
-        foreach (Futures($dfutures) as $future_head => $dfuture) {
+        foreach (new FutureIterator($dfutures) as $future_head => $dfuture) {
           list($stdout) = $dfuture->resolvex();
           $descendant_heads = array_filter(explode("\1", $stdout));
           if ($descendant_heads) {
             // This old head has at least one descendant in the push.
             $head_map[$future_head] = $descendant_heads;
           } else {
             // This old head has no descendants, so it is being deleted.
             $head_map[$future_head] = array(self::EMPTY_HASH);
           }
         }
 
         // Now, find all the new stray heads this push creates, if any. These
         // are new heads which do not descend from the old heads.
         $seen = array_fuse(array_mergev($head_map));
         foreach ($new_heads as $new_head) {
           if ($new_head === self::EMPTY_HASH) {
             // If a branch head is being deleted, don't insert it as an add.
             continue;
           }
           if (empty($seen[$new_head])) {
             $head_map[self::EMPTY_HASH][] = $new_head;
           }
         }
       } else if ($old_heads) {
         $head_map[head($old_heads)] = $new_heads;
       } else {
         $head_map[self::EMPTY_HASH] = $new_heads;
       }
 
       foreach ($head_map as $old_head => $child_heads) {
         foreach ($child_heads as $new_head) {
           if ($new_head === $old_head) {
             continue;
           }
 
           $ref_flags = 0;
           $dangerous = null;
           if ($old_head == self::EMPTY_HASH) {
             $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_ADD;
           } else {
             $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_APPEND;
           }
 
 
           $deletes_existing_head = ($new_head == self::EMPTY_HASH);
           $splits_existing_head = (count($child_heads) > 1);
           $creates_duplicate_head = ($old_head == self::EMPTY_HASH) &&
                                     (count($head_map) > 1);
 
           if ($splits_existing_head || $creates_duplicate_head) {
             $readable_child_heads = array();
             foreach ($child_heads as $child_head) {
               $readable_child_heads[] = substr($child_head, 0, 12);
             }
 
             $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DANGEROUS;
 
             if ($splits_existing_head) {
               // We're splitting an existing head into two or more heads.
               // This is dangerous, and a super bad idea. Note that we're only
               // raising this if you're actively splitting a branch head. If a
               // head split in the past, we don't consider appends to it
               // to be dangerous.
               $dangerous = pht(
                 "The change you're attempting to push splits the head of ".
                 "branch '%s' into multiple heads: %s. This is inadvisable ".
                 "and dangerous.",
                 $ref,
                 implode(', ', $readable_child_heads));
             } else {
               // We're adding a second (or more) head to a branch. The new
               // head is not a descendant of any old head.
               $dangerous = pht(
                 "The change you're attempting to push creates new, divergent ".
                 "heads for the branch '%s': %s. This is inadvisable and ".
                 "dangerous.",
                 $ref,
                 implode(', ', $readable_child_heads));
             }
           }
 
           if ($deletes_existing_head) {
             // TODO: Somewhere in here we should be setting CHANGEFLAG_REWRITE
             // if we are also creating at least one other head to replace
             // this one.
 
             // NOTE: In Git, this is a dangerous change, but it is not dangerous
             // in Mercurial. Mercurial branches are version controlled, and
             // Mercurial does not prompt you for any special flags when pushing
             // a `--close-branch` commit by default.
 
             $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
           }
 
           $ref_update = $this->newPushLog()
             ->setRefType(PhabricatorRepositoryPushLog::REFTYPE_BRANCH)
             ->setRefName($ref)
             ->setRefOld($old_head)
             ->setRefNew($new_head)
             ->setChangeFlags($ref_flags);
 
           if ($dangerous !== null) {
             $ref_update->attachDangerousChangeDescription($dangerous);
           }
 
           $ref_updates[] = $ref_update;
         }
       }
     }
 
     return $ref_updates;
   }
 
   private function findMercurialPushKeyRefUpdates() {
     $key_namespace = getenv('HG_NAMESPACE');
 
     if ($key_namespace === 'phases') {
       // Mercurial changes commit phases as part of normal push operations. We
       // just ignore these, as they don't seem to represent anything
       // interesting.
       return array();
     }
 
     $key_name = getenv('HG_KEY');
 
     $key_old = getenv('HG_OLD');
     if (!strlen($key_old)) {
       $key_old = null;
     }
 
     $key_new = getenv('HG_NEW');
     if (!strlen($key_new)) {
       $key_new = null;
     }
 
     if ($key_namespace !== 'bookmarks') {
       throw new Exception(
         pht(
           "Unknown Mercurial key namespace '%s', with key '%s' (%s -> %s). ".
           "Rejecting push.",
           $key_namespace,
           $key_name,
           coalesce($key_old, pht('null')),
           coalesce($key_new, pht('null'))));
     }
 
     if ($key_old === $key_new) {
       // We get a callback when the bookmark doesn't change. Just ignore this,
       // as it's a no-op.
       return array();
     }
 
     $ref_flags = 0;
     $merge_base = null;
     if ($key_old === null) {
       $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_ADD;
     } else if ($key_new === null) {
       $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_DELETE;
     } else {
       list($merge_base_raw) = $this->getRepository()->execxLocalCommand(
         'log --template %s --rev %s',
         '{node}',
         hgsprintf('ancestor(%s, %s)', $key_old, $key_new));
 
       if (strlen(trim($merge_base_raw))) {
         $merge_base = trim($merge_base_raw);
       }
 
       if ($merge_base && ($merge_base === $key_old)) {
         $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_APPEND;
       } else {
         $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_REWRITE;
       }
     }
 
     $ref_update = $this->newPushLog()
       ->setRefType(PhabricatorRepositoryPushLog::REFTYPE_BOOKMARK)
       ->setRefName($key_name)
       ->setRefOld(coalesce($key_old, self::EMPTY_HASH))
       ->setRefNew(coalesce($key_new, self::EMPTY_HASH))
       ->setChangeFlags($ref_flags);
 
     return array($ref_update);
   }
 
   private function findMercurialContentUpdates(array $ref_updates) {
     $content_updates = array();
 
     foreach ($this->mercurialCommits as $commit => $branches) {
       $content_updates[$commit] = $this->newPushLog()
         ->setRefType(PhabricatorRepositoryPushLog::REFTYPE_COMMIT)
         ->setRefNew($commit)
         ->setChangeFlags(PhabricatorRepositoryPushLog::CHANGEFLAG_ADD);
     }
 
     return $content_updates;
   }
 
   private function parseMercurialCommits($raw) {
     $commits_lines = explode("\2", $raw);
     $commits_lines = array_filter($commits_lines);
     $commit_map = array();
     foreach ($commits_lines as $commit_line) {
       list($node, $branch) = explode("\1", $commit_line);
       $commit_map[$node] = array($branch);
     }
 
     return $commit_map;
   }
 
   private function parseMercurialHeads($raw) {
     $heads_map = $this->parseMercurialCommits($raw);
 
     $heads = array();
     foreach ($heads_map as $commit => $branches) {
       foreach ($branches as $branch) {
         $heads[$branch][] = $commit;
       }
     }
 
     return $heads;
   }
 
 
 /* -(  Subversion  )--------------------------------------------------------- */
 
 
   private function findSubversionRefUpdates() {
     // Subversion doesn't have any kind of mutable ref metadata.
     return array();
   }
 
   private function findSubversionContentUpdates(array $ref_updates) {
     list($youngest) = execx(
       'svnlook youngest %s',
       $this->subversionRepository);
     $ref_new = (int)$youngest + 1;
 
     $ref_flags = 0;
     $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_ADD;
     $ref_flags |= PhabricatorRepositoryPushLog::CHANGEFLAG_APPEND;
 
     $ref_content = $this->newPushLog()
       ->setRefType(PhabricatorRepositoryPushLog::REFTYPE_COMMIT)
       ->setRefNew($ref_new)
       ->setChangeFlags($ref_flags);
 
     return array($ref_content);
   }
 
 
 /* -(  Internals  )---------------------------------------------------------- */
 
 
   private function newPushLog() {
     // NOTE: We generate PHIDs up front so the Herald transcripts can pick them
     // up.
     $phid = id(new PhabricatorRepositoryPushLog())->generatePHID();
 
     return PhabricatorRepositoryPushLog::initializeNewLog($this->getViewer())
       ->setPHID($phid)
       ->setRepositoryPHID($this->getRepository()->getPHID())
       ->attachRepository($this->getRepository())
       ->setEpoch(time());
   }
 
   private function newPushEvent() {
     $viewer = $this->getViewer();
     return PhabricatorRepositoryPushEvent::initializeNewEvent($viewer)
       ->setRepositoryPHID($this->getRepository()->getPHID())
       ->setRemoteAddress($this->getRemoteAddressForLog())
       ->setRemoteProtocol($this->getRemoteProtocol())
       ->setEpoch(time());
   }
 
   public function loadChangesetsForCommit($identifier) {
     $byte_limit = HeraldCommitAdapter::getEnormousByteLimit();
     $time_limit = HeraldCommitAdapter::getEnormousTimeLimit();
 
     $vcs = $this->getRepository()->getVersionControlSystem();
     switch ($vcs) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         // For git and hg, we can use normal commands.
         $drequest = DiffusionRequest::newFromDictionary(
           array(
             'repository' => $this->getRepository(),
             'user' => $this->getViewer(),
             'commit' => $identifier,
           ));
 
         $raw_diff = DiffusionRawDiffQuery::newFromDiffusionRequest($drequest)
           ->setTimeout($time_limit)
           ->setByteLimit($byte_limit)
           ->setLinesOfContext(0)
           ->loadRawDiff();
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         // TODO: This diff has 3 lines of context, which produces slightly
         // incorrect "added file content" and "removed file content" results.
         // This may also choke on binaries, but "svnlook diff" does not support
         // the "--diff-cmd" flag.
 
         // For subversion, we need to use `svnlook`.
         $future = new ExecFuture(
           'svnlook diff -t %s %s',
           $this->subversionTransaction,
           $this->subversionRepository);
 
         $future->setTimeout($time_limit);
         $future->setStdoutSizeLimit($byte_limit);
         $future->setStderrSizeLimit($byte_limit);
 
         list($raw_diff) = $future->resolvex();
         break;
       default:
         throw new Exception(pht("Unknown VCS '%s!'", $vcs));
     }
 
     if (strlen($raw_diff) >= $byte_limit) {
       throw new Exception(
         pht(
           'The raw text of this change is enormous (larger than %d '.
           'bytes). Herald can not process it.',
           $byte_limit));
     }
 
     if (!strlen($raw_diff)) {
       // If the commit is actually empty, just return no changesets.
       return array();
     }
 
     $parser = new ArcanistDiffParser();
     $changes = $parser->parseDiff($raw_diff);
     $diff = DifferentialDiff::newEphemeralFromRawChanges(
       $changes);
     return $diff->getChangesets();
   }
 
   public function loadCommitRefForCommit($identifier) {
     $repository = $this->getRepository();
     $vcs = $repository->getVersionControlSystem();
     switch ($vcs) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         return id(new DiffusionLowLevelCommitQuery())
           ->setRepository($repository)
           ->withIdentifier($identifier)
           ->execute();
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         // For subversion, we need to use `svnlook`.
         list($message) = execx(
           'svnlook log -t %s %s',
           $this->subversionTransaction,
           $this->subversionRepository);
 
         return id(new DiffusionCommitRef())
           ->setMessage($message);
         break;
       default:
         throw new Exception(pht("Unknown VCS '%s!'", $vcs));
     }
   }
 
   public function loadBranches($identifier) {
     $repository = $this->getRepository();
     $vcs = $repository->getVersionControlSystem();
     switch ($vcs) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         return idx($this->gitCommits, $identifier, array());
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         // NOTE: This will be "the branch the commit was made to", not
         // "a list of all branch heads which descend from the commit".
         // This is consistent with Mercurial, but possibly confusing.
         return idx($this->mercurialCommits, $identifier, array());
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         // Subversion doesn't have branches.
         return array();
     }
   }
 
   private function loadCommitInfoForWorker(array $all_updates) {
     $type_commit = PhabricatorRepositoryPushLog::REFTYPE_COMMIT;
 
     $map = array();
     foreach ($all_updates as $update) {
       if ($update->getRefType() != $type_commit) {
         continue;
       }
       $map[$update->getRefNew()] = array();
     }
 
     foreach ($map as $identifier => $info) {
       $ref = $this->loadCommitRefForCommit($identifier);
       $map[$identifier] += array(
         'summary'  => $ref->getSummary(),
         'branches' => $this->loadBranches($identifier),
       );
     }
 
     return $map;
   }
 
 }
diff --git a/src/applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php b/src/applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php
index ca47c04ca1..72f2d18533 100644
--- a/src/applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php
+++ b/src/applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php
@@ -1,219 +1,219 @@
 <?php
 
 /**
  * Resolves references (like short commit names, branch names, tag names, etc.)
  * into canonical, stable commit identifiers. This query works for all
  * repository types.
  */
 final class DiffusionLowLevelResolveRefsQuery
   extends DiffusionLowLevelQuery {
 
   private $refs;
 
   public function withRefs(array $refs) {
     $this->refs = $refs;
     return $this;
   }
 
   public function executeQuery() {
     if (!$this->refs) {
       return array();
     }
 
     switch ($this->getRepository()->getVersionControlSystem()) {
       case PhabricatorRepositoryType::REPOSITORY_TYPE_GIT:
         $result = $this->resolveGitRefs();
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_MERCURIAL:
         $result = $this->resolveMercurialRefs();
         break;
       case PhabricatorRepositoryType::REPOSITORY_TYPE_SVN:
         $result = $this->resolveSubversionRefs();
         break;
       default:
         throw new Exception('Unsupported repository type!');
     }
 
     return $result;
   }
 
   private function resolveGitRefs() {
     $repository = $this->getRepository();
 
     $future = $repository->getLocalCommandFuture('cat-file --batch-check');
     $future->write(implode("\n", $this->refs));
     list($stdout) = $future->resolvex();
 
     $lines = explode("\n", rtrim($stdout, "\n"));
     if (count($lines) !== count($this->refs)) {
       throw new Exception('Unexpected line count from `git cat-file`!');
     }
 
     $hits = array();
     $tags = array();
 
     $lines = array_combine($this->refs, $lines);
     foreach ($lines as $ref => $line) {
       $parts = explode(' ', $line);
       if (count($parts) < 2) {
         throw new Exception("Failed to parse `git cat-file` output: {$line}");
       }
       list($identifier, $type) = $parts;
 
       if ($type == 'missing') {
         // This is either an ambiguous reference which resolves to several
         // objects, or an invalid reference. For now, always treat it as
         // invalid. It would be nice to resolve all possibilities for
         // ambiguous references at some point, although the strategy for doing
         // so isn't clear to me.
         continue;
       }
 
       switch ($type) {
         case 'commit':
           break;
         case 'tag':
           $tags[] = $identifier;
           break;
         default:
           throw new Exception(
             "Unexpected object type from `git cat-file`: {$line}");
       }
 
       $hits[] = array(
         'ref' => $ref,
         'type' => $type,
         'identifier' => $identifier,
       );
     }
 
     $tag_map = array();
     if ($tags) {
       // If some of the refs were tags, just load every tag in order to figure
       // out which commits they map to. This might be somewhat inefficient in
       // repositories with a huge number of tags.
       $tag_refs = id(new DiffusionLowLevelGitRefQuery())
         ->setRepository($repository)
         ->withIsTag(true)
         ->executeQuery();
       foreach ($tag_refs as $tag_ref) {
         $tag_map[$tag_ref->getShortName()] = $tag_ref->getCommitIdentifier();
       }
     }
 
     $results = array();
     foreach ($hits as $hit) {
       $type = $hit['type'];
       $ref = $hit['ref'];
 
       $alternate = null;
       if ($type == 'tag') {
         $alternate = $identifier;
         $identifier = idx($tag_map, $ref);
         if (!$identifier) {
           throw new Exception("Failed to look up tag '{$ref}'!");
         }
       }
 
       $result = array(
         'type' => $type,
         'identifier' => $identifier,
       );
 
       if ($alternate !== null) {
         $result['alternate'] = $alternate;
       }
 
       $results[$ref][] = $result;
     }
 
     return $results;
   }
 
   private function resolveMercurialRefs() {
     $repository = $this->getRepository();
 
     $futures = array();
     foreach ($this->refs as $ref) {
       $futures[$ref] = $repository->getLocalCommandFuture(
         'log --template=%s --rev %s',
         '{node}',
         hgsprintf('%s', $ref));
     }
 
     $results = array();
-    foreach (Futures($futures) as $ref => $future) {
+    foreach (new FutureIterator($futures) as $ref => $future) {
       try {
         list($stdout) = $future->resolvex();
       } catch (CommandException $ex) {
         if (preg_match('/ambiguous identifier/', $ex->getStdErr())) {
           // This indicates that the ref ambiguously matched several things.
           // Eventually, it would be nice to return all of them, but it is
           // unclear how to best do that. For now, treat it as a miss instead.
           continue;
         }
         throw $ex;
       }
 
       // It doesn't look like we can figure out the type (commit/branch/rev)
       // from this output very easily. For now, just call everything a commit.
       $type = 'commit';
 
       $results[$ref][] = array(
         'type' => $type,
         'identifier' => trim($stdout),
       );
     }
 
     return $results;
   }
 
   private function resolveSubversionRefs() {
     $repository = $this->getRepository();
 
     $max_commit = id(new PhabricatorRepositoryCommit())
       ->loadOneWhere(
         'repositoryID = %d ORDER BY epoch DESC, id DESC LIMIT 1',
         $repository->getID());
     if (!$max_commit) {
       // This repository is empty or hasn't parsed yet, so none of the refs are
       // going to resolve.
       return array();
     }
 
     $max_commit_id = (int)$max_commit->getCommitIdentifier();
 
     $results = array();
     foreach ($this->refs as $ref) {
       if ($ref == 'HEAD') {
         // Resolve "HEAD" to mean "the most recent commit".
         $results[$ref][] = array(
           'type' => 'commit',
           'identifier' => $max_commit_id,
         );
         continue;
       }
 
       if (!preg_match('/^\d+$/', $ref)) {
         // This ref is non-numeric, so it doesn't resolve to anything.
         continue;
       }
 
       // Resolve other commits if we can deduce their existence.
 
       // TODO: When we import only part of a repository, we won't necessarily
       // have all of the smaller commits. Should we fail to resolve them here
       // for repositories with a subpath? It might let us simplify other things
       // elsewhere.
       if ((int)$ref <= $max_commit_id) {
         $results[$ref][] = array(
           'type' => 'commit',
           'identifier' => (int)$ref,
         );
       }
     }
 
     return $results;
   }
 
 }
diff --git a/src/applications/diviner/workflow/DivinerGenerateWorkflow.php b/src/applications/diviner/workflow/DivinerGenerateWorkflow.php
index 7a75f744ab..bc799af303 100644
--- a/src/applications/diviner/workflow/DivinerGenerateWorkflow.php
+++ b/src/applications/diviner/workflow/DivinerGenerateWorkflow.php
@@ -1,529 +1,531 @@
 <?php
 
 final class DivinerGenerateWorkflow extends DivinerWorkflow {
 
   private $atomCache;
 
   public function didConstruct() {
     $this
       ->setName('generate')
       ->setSynopsis(pht('Generate documentation.'))
       ->setArguments(
         array(
           array(
             'name' => 'clean',
             'help' => 'Clear the caches before generating documentation.',
           ),
           array(
             'name' => 'book',
             'param' => 'path',
             'help' => 'Path to a Diviner book configuration.',
           ),
         ));
   }
 
   protected function getAtomCache() {
     if (!$this->atomCache) {
       $book_root = $this->getConfig('root');
       $book_name = $this->getConfig('name');
       $cache_directory = $book_root.'/.divinercache/'.$book_name;
       $this->atomCache = new DivinerAtomCache($cache_directory);
     }
     return $this->atomCache;
   }
 
   protected function log($message) {
     $console = PhutilConsole::getConsole();
     $console->writeErr($message."\n");
   }
 
   public function execute(PhutilArgumentParser $args) {
     $book = $args->getArg('book');
     if ($book) {
       $books = array($book);
     } else {
       $cwd = getcwd();
       $this->log(pht('FINDING DOCUMENTATION BOOKS'));
       $books = id(new FileFinder($cwd))
         ->withType('f')
         ->withSuffix('book')
         ->find();
 
       if (!$books) {
         throw new PhutilArgumentUsageException(
           pht(
             "There are no Diviner '.book' files anywhere beneath the ".
             "current directory. Use '--book <book>' to specify a ".
             "documentation book to generate."));
       } else {
         $this->log(pht('Found %s book(s).', new PhutilNumber(count($books))));
       }
     }
 
     foreach ($books as $book) {
       $short_name = basename($book);
 
       $this->log(pht('Generating book "%s"...', $short_name));
       $this->generateBook($book, $args);
       $this->log(pht('Completed generation of "%s".', $short_name)."\n");
     }
   }
 
   private function generateBook($book, PhutilArgumentParser $args) {
     $this->atomCache = null;
 
     $this->readBookConfiguration($book);
 
     if ($args->getArg('clean')) {
       $this->log(pht('CLEARING CACHES'));
       $this->getAtomCache()->delete();
       $this->log(pht('Done.')."\n");
     }
 
     // The major challenge of documentation generation is one of dependency
     // management. When regenerating documentation, we want to do the smallest
     // amount of work we can, so that regenerating documentation after minor
     // changes is quick.
     //
     // ATOM CACHE
     //
     // In the first stage, we find all the direct changes to source code since
     // the last run. This stage relies on two data structures:
     //
     //  - File Hash Map: map<file_hash, node_hash>
     //  - Atom Map: map<node_hash, true>
     //
     // First, we hash all the source files in the project to detect any which
     // have changed since the previous run (i.e., their hash is not present in
     // the File Hash Map). If a file's content hash appears in the map, it has
     // not changed, so we don't need to reparse it.
     //
     // We break the contents of each file into "atoms", which represent a unit
     // of source code (like a function, method, class or file). Each atom has a
     // "node hash" based on the content of the atom: if a function definition
     // changes, the node hash of the atom changes too. The primary output of
     // the atom cache is a list of node hashes which exist in the project. This
     // is the Atom Map. The node hash depends only on the definition of the atom
     // and the atomizer implementation. It ends with an "N", for "node".
     //
     // (We need the Atom Map in addition to the File Hash Map because each file
     // may have several atoms in it (e.g., multiple functions, or a class and
     // its methods). The File Hash Map contains an exhaustive list of all atoms
     // with type "file", but not child atoms of those top-level atoms.)
     //
     // GRAPH CACHE
     //
     // We now know which atoms exist, and can compare the Atom Map to some
     // existing cache to figure out what has changed. However, this isn't
     // sufficient to figure out which documentation actually needs to be
     // regnerated, because atoms depend on other atoms. For example, if "B
     // extends A" and the definition for A changes, we need to regenerate the
     // documentation in B. Similarly, if X links to Y and Y changes, we should
     // regenerate X. (In both these cases, the documentation for the connected
     // atom may not acutally change, but in some cases it will, and the extra
     // work we need to do is generally very small compared to the size of the
     // project.)
     //
     // To figure out which other nodes have changed, we compute a "graph hash"
     // for each node. This hash combines the "node hash" with the node hashes
     // of connected nodes. Our primary output is a list of graph hashes, which
     // a documentation generator can use to easily determine what work needs
     // to be done by comparing the list with a list of cached graph hashes,
     // then generating documentation for new hashes and deleting documentation
     // for missing hashes. The graph hash ends with a "G", for "graph".
     //
     // In this stage, we rely on three data structures:
     //
     //  - Symbol Map: map<node_hash, symbol_hash>
     //  - Edge Map: map<node_hash, list<symbol_hash>>
     //  - Graph Map: map<node_hash, graph_hash>
     //
     // Calculating the graph hash requires several steps, because we need to
     // figure out which nodes an atom is attached to. The atom contains symbolic
     // references to other nodes by name (e.g., "extends SomeClass") in the form
     // of DivinerAtomRefs. We can also build a symbolic reference for any atom
     // from the atom itself. Each DivinerAtomRef generates a symbol hash,
     // which ends with an "S", for "symbol".
     //
     // First, we update the symbol map. We remove (and mark dirty) any symbols
     // associated with node hashes which no longer exist (e.g., old/dead nodes).
     // Second, we add (and mark dirty) any symbols associated with new nodes.
     // We also add edges defined by new nodes to the graph.
     //
     // We initialize a list of dirty nodes to the list of new nodes, then
     // find all nodes connected to dirty symbols and add them to the dirty
     // node list. This list now contains every node with a new or changed
     // graph hash.
     //
     // We walk the dirty list and compute the new graph hashes, adding them
     // to the graph hash map. This Graph Map can then be passed to an actual
     // documentation generator, which can compare the graph hashes to a list
     // of already-generated graph hashes and easily assess which documents need
     // to be regenerated and which can be deleted.
 
     $this->buildAtomCache();
     $this->buildGraphCache();
 
     $this->publishDocumentation($args->getArg('clean'));
   }
 
 /* -(  Atom Cache  )--------------------------------------------------------- */
 
   private function buildAtomCache() {
     $this->log(pht('BUILDING ATOM CACHE'));
 
     $file_hashes = $this->findFilesInProject();
 
     $this->log(pht('Found %d file(s) in project.', count($file_hashes)));
 
     $this->deleteDeadAtoms($file_hashes);
 
     $atomize = $this->getFilesToAtomize($file_hashes);
 
     $this->log(pht('Found %d unatomized, uncached file(s).', count($atomize)));
 
     $file_atomizers = $this->getAtomizersForFiles($atomize);
 
     $this->log(pht('Found %d file(s) to atomize.', count($file_atomizers)));
 
     $futures = $this->buildAtomizerFutures($file_atomizers);
 
     $this->log(pht('Atomizing %d file(s).', count($file_atomizers)));
 
     if ($futures) {
       $this->resolveAtomizerFutures($futures, $file_hashes);
       $this->log(pht('Atomization complete.'));
     } else {
       $this->log(pht('Atom cache is up to date, no files to atomize.'));
     }
 
     $this->log(pht('Writing atom cache.'));
 
     $this->getAtomCache()->saveAtoms();
 
     $this->log(pht('Done.')."\n");
   }
 
   private function getAtomizersForFiles(array $files) {
     $rules = $this->getRules();
     $exclude = $this->getExclude();
 
     $atomizers = array();
 
     foreach ($files as $file) {
       foreach ($exclude as $pattern) {
         if (preg_match($pattern, $file)) {
           continue 2;
         }
       }
 
       foreach ($rules as $rule => $atomizer) {
         $ok = preg_match($rule, $file);
         if ($ok === false) {
           throw new Exception(
             "Rule '{$rule}' is not a valid regular expression.");
         }
         if ($ok) {
           $atomizers[$file] = $atomizer;
           continue;
         }
       }
     }
 
     return $atomizers;
   }
 
   private function getRules() {
     $rules = $this->getConfig('rules', array(
       '/\\.diviner$/' => 'DivinerArticleAtomizer',
       '/\\.php$/' => 'DivinerPHPAtomizer',
     ));
 
     return $rules;
   }
 
   private function getExclude() {
     $exclude = (array)$this->getConfig('exclude', array());
     return $exclude;
   }
 
 
   private function findFilesInProject() {
     $raw_hashes = id(new FileFinder($this->getConfig('root')))
       ->excludePath('*/.*')
       ->withType('f')
       ->setGenerateChecksums(true)
       ->find();
 
     $version = $this->getDivinerAtomWorldVersion();
 
     $file_hashes = array();
     foreach ($raw_hashes as $file => $md5_hash) {
       $rel_file = Filesystem::readablePath($file, $this->getConfig('root'));
       // We want the hash to change if the file moves or Diviner gets updated,
       // not just if the file content changes. Derive a hash from everything
       // we care about.
       $file_hashes[$rel_file] = md5("{$rel_file}\0{$md5_hash}\0{$version}").'F';
     }
 
     return $file_hashes;
   }
 
   private function deleteDeadAtoms(array $file_hashes) {
     $atom_cache = $this->getAtomCache();
 
     $hash_to_file = array_flip($file_hashes);
     foreach ($atom_cache->getFileHashMap() as $hash => $atom) {
       if (empty($hash_to_file[$hash])) {
         $atom_cache->deleteFileHash($hash);
       }
     }
   }
 
   private function getFilesToAtomize(array $file_hashes) {
     $atom_cache = $this->getAtomCache();
 
     $atomize = array();
     foreach ($file_hashes as $file => $hash) {
       if (!$atom_cache->fileHashExists($hash)) {
         $atomize[] = $file;
       }
     }
 
     return $atomize;
   }
 
   private function buildAtomizerFutures(array $file_atomizers) {
     $atomizers = array();
     foreach ($file_atomizers as $file => $atomizer) {
       $atomizers[$atomizer][] = $file;
     }
 
     $root = dirname(phutil_get_library_root('phabricator'));
     $config_root = $this->getConfig('root');
 
     $bar = id(new PhutilConsoleProgressBar())
       ->setTotal(count($file_atomizers));
 
     $futures = array();
     foreach ($atomizers as $class => $files) {
       foreach (array_chunk($files, 32) as $chunk) {
         $future = new ExecFuture(
           '%s atomize --ugly --book %s --atomizer %s -- %Ls',
           $root.'/bin/diviner',
           $this->getBookConfigPath(),
           $class,
           $chunk);
         $future->setCWD($config_root);
 
         $futures[] = $future;
 
         $bar->update(count($chunk));
       }
     }
 
     $bar->done();
 
     return $futures;
   }
 
   private function resolveAtomizerFutures(array $futures, array $file_hashes) {
     assert_instances_of($futures, 'Future');
 
     $atom_cache = $this->getAtomCache();
     $bar = id(new PhutilConsoleProgressBar())
       ->setTotal(count($futures));
-    foreach (Futures($futures)->limit(4) as $key => $future) {
+    $futures = id(new FutureIterator($futures))
+      ->limit(4);
+    foreach ($futures as $key => $future) {
       try {
         $atoms = $future->resolveJSON();
 
         foreach ($atoms as $atom) {
           if ($atom['type'] == DivinerAtom::TYPE_FILE) {
             $file_hash = $file_hashes[$atom['file']];
             $atom_cache->addFileHash($file_hash, $atom['hash']);
           }
           $atom_cache->addAtom($atom);
         }
       } catch (Exception $e) {
         phlog($e);
       }
 
       $bar->update(1);
     }
     $bar->done();
   }
 
 
   /**
    * Get a global version number, which changes whenever any atom or atomizer
    * implementation changes in a way which is not backward-compatible.
    */
   private function getDivinerAtomWorldVersion() {
     $version = array();
     $version['atom'] = DivinerAtom::getAtomSerializationVersion();
     $version['rules'] = $this->getRules();
 
     $atomizers = id(new PhutilSymbolLoader())
       ->setAncestorClass('DivinerAtomizer')
       ->setConcreteOnly(true)
       ->selectAndLoadSymbols();
 
     $atomizer_versions = array();
     foreach ($atomizers as $atomizer) {
       $atomizer_versions[$atomizer['name']] = call_user_func(
         array(
           $atomizer['name'],
           'getAtomizerVersion',
         ));
     }
 
     ksort($atomizer_versions);
     $version['atomizers'] = $atomizer_versions;
 
     return md5(serialize($version));
   }
 
 
 /* -(  Graph Cache  )-------------------------------------------------------- */
 
 
   private function buildGraphCache() {
     $this->log(pht('BUILDING GRAPH CACHE'));
 
     $atom_cache = $this->getAtomCache();
     $symbol_map = $atom_cache->getSymbolMap();
     $atoms = $atom_cache->getAtomMap();
 
     $dirty_symbols = array();
     $dirty_nhashes = array();
 
     $del_atoms = array_diff_key($symbol_map, $atoms);
     $this->log(pht('Found %d obsolete atom(s) in graph.', count($del_atoms)));
     foreach ($del_atoms as $nhash => $shash) {
       $atom_cache->deleteSymbol($nhash);
       $dirty_symbols[$shash] = true;
 
       $atom_cache->deleteEdges($nhash);
       $atom_cache->deleteGraph($nhash);
     }
 
     $new_atoms = array_diff_key($atoms, $symbol_map);
     $this->log(pht('Found %d new atom(s) in graph.', count($new_atoms)));
     foreach ($new_atoms as $nhash => $ignored) {
       $shash = $this->computeSymbolHash($nhash);
       $atom_cache->addSymbol($nhash, $shash);
       $dirty_symbols[$shash] = true;
 
       $atom_cache->addEdges(
         $nhash,
         $this->getEdges($nhash));
 
       $dirty_nhashes[$nhash] = true;
     }
 
     $this->log(pht('Propagating changes through the graph.'));
 
     // Find all the nodes which point at a dirty node, and dirty them. Then
     // find all the nodes which point at those nodes and dirty them, and so
     // on. (This is slightly overkill since we probably don't need to propagate
     // dirtiness across documentation "links" between symbols, but we do want
     // to propagate it across "extends", and we suffer only a little bit of
     // collateral damage by over-dirtying as long as the documentation isn't
     // too well-connected.)
 
     $symbol_stack = array_keys($dirty_symbols);
     while ($symbol_stack) {
       $symbol_hash = array_pop($symbol_stack);
 
       foreach ($atom_cache->getEdgesWithDestination($symbol_hash) as $edge) {
         $dirty_nhashes[$edge] = true;
         $src_hash = $this->computeSymbolHash($edge);
         if (empty($dirty_symbols[$src_hash])) {
           $dirty_symbols[$src_hash] = true;
           $symbol_stack[] = $src_hash;
         }
       }
     }
 
     $this->log(pht('Found %d affected atoms.', count($dirty_nhashes)));
 
     foreach ($dirty_nhashes as $nhash => $ignored) {
       $atom_cache->addGraph($nhash, $this->computeGraphHash($nhash));
     }
 
     $this->log(pht('Writing graph cache.'));
 
     $atom_cache->saveGraph();
     $atom_cache->saveEdges();
     $atom_cache->saveSymbols();
 
     $this->log(pht('Done.')."\n");
   }
 
   private function computeSymbolHash($node_hash) {
     $atom_cache = $this->getAtomCache();
     $atom = $atom_cache->getAtom($node_hash);
 
     if (!$atom) {
       throw new Exception("No such atom with node hash '{$node_hash}'!");
     }
 
     $ref = DivinerAtomRef::newFromDictionary($atom['ref']);
     return $ref->toHash();
   }
 
   private function getEdges($node_hash) {
     $atom_cache = $this->getAtomCache();
     $atom = $atom_cache->getAtom($node_hash);
 
     $refs = array();
 
     // Make the atom depend on its own symbol, so that all atoms with the same
     // symbol are dirtied (e.g., if a codebase defines the function "f()"
     // several times, all of them should be dirtied when one is dirtied).
     $refs[DivinerAtomRef::newFromDictionary($atom)->toHash()] = true;
 
     foreach (array_merge($atom['extends'], $atom['links']) as $ref_dict) {
       $ref = DivinerAtomRef::newFromDictionary($ref_dict);
       if ($ref->getBook() == $atom['book']) {
         $refs[$ref->toHash()] = true;
       }
     }
 
     return array_keys($refs);
   }
 
   private function computeGraphHash($node_hash) {
     $atom_cache = $this->getAtomCache();
     $atom = $atom_cache->getAtom($node_hash);
 
     $edges = $this->getEdges($node_hash);
     sort($edges);
 
     $inputs = array(
       'atomHash' => $atom['hash'],
       'edges' => $edges,
     );
 
     return md5(serialize($inputs)).'G';
   }
 
 
   private function publishDocumentation($clean) {
     $atom_cache = $this->getAtomCache();
     $graph_map = $atom_cache->getGraphMap();
 
     $this->log(pht('PUBLISHING DOCUMENTATION'));
 
     $publisher = new DivinerLivePublisher();
     $publisher->setDropCaches($clean);
     $publisher->setConfig($this->getAllConfig());
     $publisher->setAtomCache($atom_cache);
     $publisher->setRenderer(new DivinerDefaultRenderer());
     $publisher->publishAtoms(array_values($graph_map));
 
     $this->log(pht('Done.'));
   }
 
 
 }
diff --git a/src/applications/doorkeeper/bridge/DoorkeeperBridgeAsana.php b/src/applications/doorkeeper/bridge/DoorkeeperBridgeAsana.php
index 79e711e00a..4e32239793 100644
--- a/src/applications/doorkeeper/bridge/DoorkeeperBridgeAsana.php
+++ b/src/applications/doorkeeper/bridge/DoorkeeperBridgeAsana.php
@@ -1,129 +1,129 @@
 <?php
 
 final class DoorkeeperBridgeAsana extends DoorkeeperBridge {
 
   const APPTYPE_ASANA   = 'asana';
   const APPDOMAIN_ASANA = 'asana.com';
   const OBJTYPE_TASK    = 'asana:task';
 
   public function canPullRef(DoorkeeperObjectRef $ref) {
     if ($ref->getApplicationType() != self::APPTYPE_ASANA) {
       return false;
     }
 
     if ($ref->getApplicationDomain() != self::APPDOMAIN_ASANA) {
       return false;
     }
 
     $types = array(
       self::OBJTYPE_TASK => true,
     );
 
     return isset($types[$ref->getObjectType()]);
   }
 
   public function pullRefs(array $refs) {
 
     $id_map = mpull($refs, 'getObjectID', 'getObjectKey');
     $viewer = $this->getViewer();
 
     $provider = PhabricatorAsanaAuthProvider::getAsanaProvider();
     if (!$provider) {
       return;
     }
 
     $accounts = id(new PhabricatorExternalAccountQuery())
       ->setViewer($viewer)
       ->withUserPHIDs(array($viewer->getPHID()))
       ->withAccountTypes(array($provider->getProviderType()))
       ->withAccountDomains(array($provider->getProviderDomain()))
       ->requireCapabilities(
         array(
           PhabricatorPolicyCapability::CAN_VIEW,
           PhabricatorPolicyCapability::CAN_EDIT,
         ))
       ->execute();
 
     if (!$accounts) {
       return $this->didFailOnMissingLink();
     }
 
     // TODO: If the user has several linked Asana accounts, we just pick the
     // first one arbitrarily. We might want to try using all of them or do
     // something with more finesse. There's no UI way to link multiple accounts
     // right now so this is currently moot.
     $account = head($accounts);
 
     $token = $provider->getOAuthAccessToken($account);
     if (!$token) {
       return;
     }
 
     $template = id(new PhutilAsanaFuture())
       ->setAccessToken($token);
 
     $futures = array();
     foreach ($id_map as $key => $id) {
       $futures[$key] = id(clone $template)
         ->setRawAsanaQuery("tasks/{$id}");
     }
 
     $results = array();
     $failed = array();
-    foreach (Futures($futures) as $key => $future) {
+    foreach (new FutureIterator($futures) as $key => $future) {
       try {
         $results[$key] = $future->resolve();
       } catch (Exception $ex) {
         if (($ex instanceof HTTPFutureResponseStatus) &&
             ($ex->getStatusCode() == 404)) {
           // This indicates that the object has been deleted (or never existed,
           // or isn't visible to the current user) but it's a successful sync of
           // an object which isn't visible.
         } else {
           // This is something else, so consider it a synchronization failure.
           phlog($ex);
           $failed[$key] = $ex;
         }
       }
     }
 
     foreach ($refs as $ref) {
       $ref->setAttribute('name', pht('Asana Task %s', $ref->getObjectID()));
 
       $did_fail = idx($failed, $ref->getObjectKey());
       if ($did_fail) {
         $ref->setSyncFailed(true);
         continue;
       }
 
       $result = idx($results, $ref->getObjectKey());
       if (!$result) {
         continue;
       }
 
       $ref->setIsVisible(true);
       $ref->setAttribute('asana.data', $result);
       $ref->setAttribute('fullname', pht('Asana: %s', $result['name']));
       $ref->setAttribute('title', $result['name']);
       $ref->setAttribute('description', $result['notes']);
 
       $obj = $ref->getExternalObject();
       if ($obj->getID()) {
         continue;
       }
 
       $this->fillObjectFromData($obj, $result);
 
       $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
         $obj->save();
       unset($unguarded);
     }
   }
 
   public function fillObjectFromData(DoorkeeperExternalObject $obj, $result) {
     $id = $result['id'];
     $uri = "https://app.asana.com/0/{$id}/{$id}";
     $obj->setObjectURI($uri);
   }
 
 }
diff --git a/src/applications/doorkeeper/bridge/DoorkeeperBridgeJIRA.php b/src/applications/doorkeeper/bridge/DoorkeeperBridgeJIRA.php
index 6349943770..c9b40d2e72 100644
--- a/src/applications/doorkeeper/bridge/DoorkeeperBridgeJIRA.php
+++ b/src/applications/doorkeeper/bridge/DoorkeeperBridgeJIRA.php
@@ -1,148 +1,148 @@
 <?php
 
 final class DoorkeeperBridgeJIRA extends DoorkeeperBridge {
 
   const APPTYPE_JIRA = 'jira';
   const OBJTYPE_ISSUE = 'jira:issue';
 
   public function canPullRef(DoorkeeperObjectRef $ref) {
     if ($ref->getApplicationType() != self::APPTYPE_JIRA) {
       return false;
     }
 
     $types = array(
       self::OBJTYPE_ISSUE => true,
     );
 
     return isset($types[$ref->getObjectType()]);
   }
 
   public function pullRefs(array $refs) {
 
     $id_map = mpull($refs, 'getObjectID', 'getObjectKey');
     $viewer = $this->getViewer();
 
     $provider = PhabricatorJIRAAuthProvider::getJIRAProvider();
     if (!$provider) {
       return;
     }
 
     $accounts = id(new PhabricatorExternalAccountQuery())
       ->setViewer($viewer)
       ->withUserPHIDs(array($viewer->getPHID()))
       ->withAccountTypes(array($provider->getProviderType()))
       ->requireCapabilities(
         array(
           PhabricatorPolicyCapability::CAN_VIEW,
           PhabricatorPolicyCapability::CAN_EDIT,
         ))
       ->execute();
 
     if (!$accounts) {
       return $this->didFailOnMissingLink();
     }
 
     // TODO: When we support multiple JIRA instances, we need to disambiguate
     // issues (perhaps with additional configuration) or cast a wide net
     // (by querying all instances). For now, just query the one instance.
     $account = head($accounts);
 
     $futures = array();
     foreach ($id_map as $key => $id) {
       $futures[$key] = $provider->newJIRAFuture(
         $account,
         'rest/api/2/issue/'.phutil_escape_uri($id),
         'GET');
     }
 
     $results = array();
     $failed = array();
-    foreach (Futures($futures) as $key => $future) {
+    foreach (new FutureIterator($futures) as $key => $future) {
       try {
         $results[$key] = $future->resolveJSON();
       } catch (Exception $ex) {
         if (($ex instanceof HTTPFutureResponseStatus) &&
             ($ex->getStatusCode() == 404)) {
           // This indicates that the object has been deleted (or never existed,
           // or isn't visible to the current user) but it's a successful sync of
           // an object which isn't visible.
         } else {
           // This is something else, so consider it a synchronization failure.
           phlog($ex);
           $failed[$key] = $ex;
         }
       }
     }
 
     foreach ($refs as $ref) {
       $ref->setAttribute('name', pht('JIRA %s', $ref->getObjectID()));
 
       $did_fail = idx($failed, $ref->getObjectKey());
       if ($did_fail) {
         $ref->setSyncFailed(true);
         continue;
       }
 
       $result = idx($results, $ref->getObjectKey());
       if (!$result) {
         continue;
       }
 
       $fields = idx($result, 'fields', array());
 
       $ref->setIsVisible(true);
       $ref->setAttribute(
         'fullname',
         pht('JIRA %s %s', $result['key'], idx($fields, 'summary')));
 
       $ref->setAttribute('title', idx($fields, 'summary'));
       $ref->setAttribute('description', idx($result, 'description'));
 
       $obj = $ref->getExternalObject();
       if ($obj->getID()) {
         continue;
       }
 
       $this->fillObjectFromData($obj, $result);
 
       $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
         $obj->save();
       unset($unguarded);
     }
   }
 
   public function fillObjectFromData(DoorkeeperExternalObject $obj, $result) {
     // Convert the "self" URI, which points at the REST endpoint, into a
     // browse URI.
     $self = idx($result, 'self');
     $object_id = $obj->getObjectID();
 
     $uri = self::getJIRAIssueBrowseURIFromJIRARestURI($self, $object_id);
     if ($uri !== null) {
       $obj->setObjectURI($uri);
     }
   }
 
   public static function getJIRAIssueBrowseURIFromJIRARestURI(
     $uri,
     $object_id) {
 
     $uri = new PhutilURI($uri);
 
     // The JIRA install might not be at the domain root, so we may need to
     // keep an initial part of the path, like "/jira/". Find the API specific
     // part of the URI, strip it off, then replace it with the web version.
     $path = $uri->getPath();
     $pos = strrpos($path, 'rest/api/2/issue/');
     if ($pos === false) {
       return null;
     }
 
     $path = substr($path, 0, $pos);
     $path = $path.'browse/'.$object_id;
     $uri->setPath($path);
 
     return (string)$uri;
   }
 
 }
diff --git a/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php b/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
index 3933cd5086..5057097fac 100644
--- a/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
+++ b/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
@@ -1,250 +1,250 @@
 <?php
 
 abstract class HarbormasterBuildStepImplementation {
 
   public static function getImplementations() {
     return id(new PhutilSymbolLoader())
       ->setAncestorClass('HarbormasterBuildStepImplementation')
       ->loadObjects();
   }
 
   public static function getImplementation($class) {
     $base = idx(self::getImplementations(), $class);
 
     if ($base) {
       return (clone $base);
     }
 
     return null;
   }
 
   public static function requireImplementation($class) {
     if (!$class) {
       throw new Exception(pht('No implementation is specified!'));
     }
 
     $implementation = self::getImplementation($class);
     if (!$implementation) {
       throw new Exception(pht('No such implementation "%s" exists!', $class));
     }
 
     return $implementation;
   }
 
   /**
    * The name of the implementation.
    */
   abstract public function getName();
 
   /**
    * The generic description of the implementation.
    */
   public function getGenericDescription() {
     return '';
   }
 
   /**
    * The description of the implementation, based on the current settings.
    */
   public function getDescription() {
     return $this->getGenericDescription();
   }
 
   /**
    * Run the build target against the specified build.
    */
   abstract public function execute(
     HarbormasterBuild $build,
     HarbormasterBuildTarget $build_target);
 
   /**
    * Gets the settings for this build step.
    */
   public function getSettings() {
     return $this->settings;
   }
 
   public function getSetting($key, $default = null) {
     return idx($this->settings, $key, $default);
   }
 
   /**
    * Loads the settings for this build step implementation from a build
    * step or target.
    */
   public final function loadSettings($build_object) {
     $this->settings = $build_object->getDetails();
     return $this;
   }
 
   /**
    * Return the name of artifacts produced by this command.
    *
    * Something like:
    *
    *   return array(
    *     'some_name_input_by_user' => 'host');
    *
    * Future steps will calculate all available artifact mappings
    * before them and filter on the type.
    *
    * @return array The mappings of artifact names to their types.
    */
   public function getArtifactInputs() {
     return array();
   }
 
   public function getArtifactOutputs() {
     return array();
   }
 
   public function getDependencies(HarbormasterBuildStep $build_step) {
     $dependencies = $build_step->getDetail('dependsOn', array());
 
     $inputs = $build_step->getStepImplementation()->getArtifactInputs();
     $inputs = ipull($inputs, null, 'key');
 
     $artifacts = $this->getAvailableArtifacts(
       $build_step->getBuildPlan(),
       $build_step,
       null);
 
     foreach ($artifacts as $key => $type) {
       if (!array_key_exists($key, $inputs)) {
         unset($artifacts[$key]);
       }
     }
 
     $artifact_steps = ipull($artifacts, 'step');
     $artifact_steps = mpull($artifact_steps, 'getPHID');
 
     $dependencies = array_merge($dependencies, $artifact_steps);
 
     return $dependencies;
   }
 
   /**
    * Returns a list of all artifacts made available in the build plan.
    */
   public static function getAvailableArtifacts(
     HarbormasterBuildPlan $build_plan,
     $current_build_step,
     $artifact_type) {
 
     $steps = id(new HarbormasterBuildStepQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())
       ->withBuildPlanPHIDs(array($build_plan->getPHID()))
       ->execute();
 
     $artifacts = array();
 
     $artifact_arrays = array();
     foreach ($steps as $step) {
       if ($current_build_step !== null &&
         $step->getPHID() === $current_build_step->getPHID()) {
 
         continue;
       }
 
       $implementation = $step->getStepImplementation();
       $array = $implementation->getArtifactOutputs();
       $array = ipull($array, 'type', 'key');
       foreach ($array as $name => $type) {
         if ($type !== $artifact_type && $artifact_type !== null) {
           continue;
         }
         $artifacts[$name] = array('type' => $type, 'step' => $step);
       }
     }
 
     return $artifacts;
   }
 
   /**
    * Convert a user-provided string with variables in it, like:
    *
    *   ls ${dirname}
    *
    * ...into a string with variables merged into it safely:
    *
    *   ls 'dir with spaces'
    *
    * @param string Name of a `vxsprintf` function, like @{function:vcsprintf}.
    * @param string User-provided pattern string containing `${variables}`.
    * @param dict   List of available replacement variables.
    * @return string String with variables replaced safely into it.
    */
   protected function mergeVariables($function, $pattern, array $variables) {
     $regexp = '/\\$\\{(?P<name>[a-z\\.]+)\\}/';
 
     $matches = null;
     preg_match_all($regexp, $pattern, $matches);
 
     $argv = array();
     foreach ($matches['name'] as $name) {
       if (!array_key_exists($name, $variables)) {
         throw new Exception(pht("No such variable '%s'!", $name));
       }
       $argv[] = $variables[$name];
     }
 
     $pattern = str_replace('%', '%%', $pattern);
     $pattern = preg_replace($regexp, '%s', $pattern);
 
     return call_user_func($function, $pattern, $argv);
   }
 
   public function getFieldSpecifications() {
     return array();
   }
 
   protected function formatSettingForDescription($key, $default = null) {
     return $this->formatValueForDescription($this->getSetting($key, $default));
   }
 
   protected function formatValueForDescription($value) {
     if (strlen($value)) {
       return phutil_tag('strong', array(), $value);
     } else {
       return phutil_tag('em', array(), pht('(null)'));
     }
   }
 
   public function supportsWaitForMessage() {
     return false;
   }
 
   public function shouldWaitForMessage(HarbormasterBuildTarget $target) {
     if (!$this->supportsWaitForMessage()) {
       return false;
     }
 
     return (bool)$target->getDetail('builtin.wait-for-message');
   }
 
   protected function shouldAbort(
     HarbormasterBuild $build,
     HarbormasterBuildTarget $target) {
 
     return $build->getBuildGeneration() !== $target->getBuildGeneration();
   }
 
   protected function resolveFuture(
     HarbormasterBuild $build,
     HarbormasterBuildTarget $target,
     Future $future) {
 
-    $futures = Futures(array($future));
+    $futures = new FutureIterator(array($future));
     foreach ($futures->setUpdateInterval(5) as $key => $future) {
       if ($future === null) {
         $build->reload();
         if ($this->shouldAbort($build, $target)) {
           throw new HarbormasterBuildAbortedException();
         }
       } else {
         return $future->resolve();
       }
     }
   }
 
 }
diff --git a/src/applications/harbormaster/step/HarbormasterCommandBuildStepImplementation.php b/src/applications/harbormaster/step/HarbormasterCommandBuildStepImplementation.php
index 806e311083..14fc65a76c 100644
--- a/src/applications/harbormaster/step/HarbormasterCommandBuildStepImplementation.php
+++ b/src/applications/harbormaster/step/HarbormasterCommandBuildStepImplementation.php
@@ -1,144 +1,144 @@
 <?php
 
 final class HarbormasterCommandBuildStepImplementation
   extends HarbormasterBuildStepImplementation {
 
   private $platform;
 
   public function getName() {
     return pht('Run Command');
   }
 
   public function getGenericDescription() {
     return pht('Run a command on Drydock host.');
   }
 
   public function getDescription() {
     return pht(
       'Run command %s on host %s.',
       $this->formatSettingForDescription('command'),
       $this->formatSettingForDescription('hostartifact'));
   }
 
   public function escapeCommand($pattern, array $args) {
     array_unshift($args, $pattern);
 
     $mode = PhutilCommandString::MODE_DEFAULT;
     if ($this->platform == 'windows') {
       $mode = PhutilCommandString::MODE_POWERSHELL;
     }
 
     return id(new PhutilCommandString($args))
       ->setEscapingMode($mode);
   }
 
   public function execute(
     HarbormasterBuild $build,
     HarbormasterBuildTarget $build_target) {
 
     $settings = $this->getSettings();
     $variables = $build_target->getVariables();
 
     $artifact = $build->loadArtifact($settings['hostartifact']);
 
     $lease = $artifact->loadDrydockLease();
 
     $this->platform = $lease->getAttribute('platform');
 
     $command = $this->mergeVariables(
       array($this, 'escapeCommand'),
       $settings['command'],
       $variables);
 
     $this->platform = null;
 
     $interface = $lease->getInterface('command');
 
     $future = $interface->getExecFuture('%C', $command);
 
     $log_stdout = $build->createLog($build_target, 'remote', 'stdout');
     $log_stderr = $build->createLog($build_target, 'remote', 'stderr');
 
     $start_stdout = $log_stdout->start();
     $start_stderr = $log_stderr->start();
 
     $build_update = 5;
 
     // Read the next amount of available output every second.
-    $futures = Futures(array($future));
+    $futures = new FutureIterator(array($future));
     foreach ($futures->setUpdateInterval(1) as $key => $future_iter) {
       if ($future_iter === null) {
 
         // Check to see if we should abort.
         if ($build_update <= 0) {
           $build->reload();
           if ($this->shouldAbort($build, $build_target)) {
             $future->resolveKill();
             throw new HarbormasterBuildAbortedException();
           } else {
             $build_update = 5;
           }
         } else {
           $build_update -= 1;
         }
 
         // Command is still executing.
 
         // Read more data as it is available.
         list($stdout, $stderr) = $future->read();
         $log_stdout->append($stdout);
         $log_stderr->append($stderr);
         $future->discardBuffers();
       } else {
         // Command execution is complete.
 
         // Get the return value so we can log that as well.
         list($err) = $future->resolve();
 
         // Retrieve the last few bits of information.
         list($stdout, $stderr) = $future->read();
         $log_stdout->append($stdout);
         $log_stderr->append($stderr);
         $future->discardBuffers();
 
         break;
       }
     }
 
     $log_stdout->finalize($start_stdout);
     $log_stderr->finalize($start_stderr);
 
     if ($err) {
       throw new HarbormasterBuildFailureException();
     }
   }
 
   public function getArtifactInputs() {
     return array(
       array(
         'name'  => pht('Run on Host'),
         'key'   => $this->getSetting('hostartifact'),
         'type'  => HarbormasterBuildArtifact::TYPE_HOST,
       ),
     );
   }
 
   public function getFieldSpecifications() {
     return array(
       'command' => array(
         'name' => pht('Command'),
         'type' => 'text',
         'required' => true,
         'caption' => pht(
           'Under Windows, this is executed under PowerShell.'.
           'Under UNIX, this is executed using the user\'s shell.'),
       ),
       'hostartifact' => array(
         'name' => pht('Host'),
         'type' => 'text',
         'required' => true,
       ),
     );
   }
 
 }
diff --git a/src/infrastructure/internationalization/management/PhabricatorInternationalizationManagementExtractWorkflow.php b/src/infrastructure/internationalization/management/PhabricatorInternationalizationManagementExtractWorkflow.php
index 6aca557188..e2819d1f28 100644
--- a/src/infrastructure/internationalization/management/PhabricatorInternationalizationManagementExtractWorkflow.php
+++ b/src/infrastructure/internationalization/management/PhabricatorInternationalizationManagementExtractWorkflow.php
@@ -1,99 +1,102 @@
 <?php
 
 final class PhabricatorInternationalizationManagementExtractWorkflow
   extends PhabricatorInternationalizationManagementWorkflow {
 
   public function didConstruct() {
     $this
       ->setName('extract')
       ->setSynopsis(pht('Extract translatable strings.'))
       ->setArguments(
         array(
           array(
             'name' => 'paths',
             'wildcard' => true,
           ),
         ));
   }
 
   public function execute(PhutilArgumentParser $args) {
     $console = PhutilConsole::getConsole();
     $paths = $args->getArg('paths');
 
     $futures = array();
     foreach ($paths as $path) {
       $root = Filesystem::resolvePath($path);
       $path_files = id(new FileFinder($root))
         ->withType('f')
         ->withSuffix('php')
         ->find();
 
       foreach ($path_files as $file) {
         $full_path = $root.DIRECTORY_SEPARATOR.$file;
         $data = Filesystem::readFile($full_path);
         $futures[$full_path] = xhpast_get_parser_future($data);
       }
     }
 
     $console->writeOut(
       "%s\n",
       pht('Found %s file(s)...', new PhutilNumber(count($futures))));
 
     $results = array();
 
     $bar = id(new PhutilConsoleProgressBar())
       ->setTotal(count($futures));
-    foreach (Futures($futures)->limit(8) as $full_path => $future) {
+
+    $futures = id(new FutureIterator($futures))
+      ->limit(8);
+    foreach ($futures as $full_path => $future) {
       $bar->update(1);
 
       $tree = XHPASTTree::newFromDataAndResolvedExecFuture(
         Filesystem::readFile($full_path),
         $future->resolve());
 
       $root = $tree->getRootNode();
       $calls = $root->selectDescendantsOfType('n_FUNCTION_CALL');
       foreach ($calls as $call) {
         $name = $call->getChildByIndex(0)->getConcreteString();
         if ($name == 'pht') {
           $params = $call->getChildByIndex(1, 'n_CALL_PARAMETER_LIST');
           $string_node = $params->getChildByIndex(0);
           $string_line = $string_node->getLineNumber();
           try {
             $string_value = $string_node->evalStatic();
 
             $results[$string_value][] = array(
               'file' => Filesystem::readablePath($full_path),
               'line' => $string_line,
             );
           } catch (Exception $ex) {
             // TODO: Deal with this junks.
           }
         }
       }
 
       $tree->dispose();
     }
     $bar->done();
 
     ksort($results);
 
     $out = array();
     $out[] = '<?php';
     $out[] = '// @nolint';
     $out[] = 'return array(';
     foreach ($results as $string => $locations) {
       foreach ($locations as $location) {
         $out[] = '  // '.$location['file'].':'.$location['line'];
       }
       $out[] = "  '".addcslashes($string, "\0..\37\\'\177..\377")."' => null,";
       $out[] = null;
     }
     $out[] = ');';
     $out[] = null;
 
     echo implode("\n", $out);
 
     return 0;
   }
 
 }
diff --git a/src/infrastructure/lint/linter/PhabricatorJavelinLinter.php b/src/infrastructure/lint/linter/PhabricatorJavelinLinter.php
index c69d8aacbc..4a2298a72a 100644
--- a/src/infrastructure/lint/linter/PhabricatorJavelinLinter.php
+++ b/src/infrastructure/lint/linter/PhabricatorJavelinLinter.php
@@ -1,280 +1,280 @@
 <?php
 
 final class PhabricatorJavelinLinter extends ArcanistLinter {
 
   private $symbols = array();
 
   private $symbolsBinary;
   private $haveWarnedAboutBinary;
 
   const LINT_PRIVATE_ACCESS = 1;
   const LINT_MISSING_DEPENDENCY = 2;
   const LINT_UNNECESSARY_DEPENDENCY = 3;
   const LINT_UNKNOWN_DEPENDENCY = 4;
   const LINT_MISSING_BINARY = 5;
 
   public function getInfoName() {
     return 'Javelin Linter';
   }
 
   public function getInfoDescription() {
     return pht(
       'This linter is intended for use with the Javelin JS library and '.
       'extensions. Use `javelinsymbols` to run Javelin rules on Javascript '.
       'source files.');
   }
 
   private function getBinaryPath() {
     if ($this->symbolsBinary === null) {
       list($err, $stdout) = exec_manual('which javelinsymbols');
       $this->symbolsBinary = ($err ? false : rtrim($stdout));
     }
     return $this->symbolsBinary;
   }
 
   public function willLintPaths(array $paths) {
     if (!$this->getBinaryPath()) {
       return;
     }
 
     $root = dirname(phutil_get_library_root('phabricator'));
     require_once $root.'/scripts/__init_script__.php';
 
     $futures = array();
     foreach ($paths as $path) {
       if ($this->shouldIgnorePath($path)) {
         continue;
       }
 
       $future = $this->newSymbolsFuture($path);
       $futures[$path] = $future;
     }
 
-    foreach (Futures($futures)->limit(8) as $path => $future) {
+    foreach (id(new FutureIterator($futures))->limit(8) as $path => $future) {
       $this->symbols[$path] = $future->resolvex();
     }
   }
 
   public function getLinterName() {
     return 'JAVELIN';
   }
 
   public function getLinterConfigurationName() {
     return 'javelin';
   }
 
   public function getLintSeverityMap() {
     return array(
       self::LINT_MISSING_BINARY => ArcanistLintSeverity::SEVERITY_WARNING,
     );
   }
 
   public function getLintNameMap() {
     return array(
       self::LINT_PRIVATE_ACCESS => 'Private Method/Member Access',
       self::LINT_MISSING_DEPENDENCY => 'Missing Javelin Dependency',
       self::LINT_UNNECESSARY_DEPENDENCY => 'Unnecessary Javelin Dependency',
       self::LINT_UNKNOWN_DEPENDENCY => 'Unknown Javelin Dependency',
       self::LINT_MISSING_BINARY => '`javelinsymbols` Not In Path',
     );
   }
 
   public function getCacheGranularity() {
     return ArcanistLinter::GRANULARITY_REPOSITORY;
   }
 
   public function getCacheVersion() {
     $version = '0';
     $binary_path = $this->getBinaryPath();
     if ($binary_path) {
       $version .= '-'.md5_file($binary_path);
     }
     return $version;
   }
 
   private function shouldIgnorePath($path) {
     return preg_match('@/__tests__/|externals/javelin/docs/@', $path);
   }
 
   public function lintPath($path) {
     if ($this->shouldIgnorePath($path)) {
       return;
     }
 
     if (!$this->symbolsBinary) {
       if (!$this->haveWarnedAboutBinary) {
         $this->haveWarnedAboutBinary = true;
         // TODO: Write build documentation for the Javelin binaries and point
         // the user at it.
         $this->raiseLintAtLine(
           1,
           0,
           self::LINT_MISSING_BINARY,
           "The 'javelinsymbols' binary in the Javelin project is not ".
           "available in \$PATH, so the Javelin linter can't run. This ".
           "isn't a big concern, but means some Javelin problems can't be ".
           "automatically detected.");
       }
       return;
     }
 
     list($uses, $installs) = $this->getUsedAndInstalledSymbolsForPath($path);
     foreach ($uses as $symbol => $line) {
       $parts = explode('.', $symbol);
       foreach ($parts as $part) {
         if ($part[0] == '_' && $part[1] != '_') {
           $base = implode('.', array_slice($parts, 0, 2));
           if (!array_key_exists($base, $installs)) {
             $this->raiseLintAtLine(
               $line,
               0,
               self::LINT_PRIVATE_ACCESS,
               "This file accesses private symbol '{$symbol}' across file ".
               "boundaries. You may only access private members and methods ".
               "from the file where they are defined.");
           }
           break;
         }
       }
     }
 
     if ($this->getEngine()->getCommitHookMode()) {
       // Don't do the dependency checks in commit-hook mode because we won't
       // have an available working copy.
       return;
     }
 
     $external_classes = array();
     foreach ($uses as $symbol => $line) {
       $parts = explode('.', $symbol);
       $class = implode('.', array_slice($parts, 0, 2));
       if (!array_key_exists($class, $external_classes) &&
           !array_key_exists($class, $installs)) {
         $external_classes[$class] = $line;
       }
     }
 
     $celerity = CelerityResourceMap::getNamedInstance('phabricator');
 
     $path = preg_replace(
       '@^externals/javelinjs/src/@',
       'webroot/rsrc/js/javelin/',
       $path);
     $need = $external_classes;
 
     $resource_name = substr($path, strlen('webroot/'));
     $requires = $celerity->getRequiredSymbolsForName($resource_name);
     if (!$requires) {
       $requires = array();
     }
 
     foreach ($requires as $key => $requires_symbol) {
       $requires_name = $celerity->getResourceNameForSymbol($requires_symbol);
       if ($requires_name === null) {
         $this->raiseLintAtLine(
           0,
           0,
           self::LINT_UNKNOWN_DEPENDENCY,
           "This file @requires component '{$requires_symbol}', but it does ".
           "not exist. You may need to rebuild the Celerity map.");
         unset($requires[$key]);
         continue;
       }
 
       if (preg_match('/\\.css$/', $requires_name)) {
         // If JS requires CSS, just assume everything is fine.
         unset($requires[$key]);
       } else {
         $symbol_path = 'webroot/'.$requires_name;
         list($ignored, $req_install) = $this->getUsedAndInstalledSymbolsForPath(
           $symbol_path);
         if (array_intersect_key($req_install, $external_classes)) {
           $need = array_diff_key($need, $req_install);
           unset($requires[$key]);
         }
       }
     }
 
     foreach ($need as $class => $line) {
       $this->raiseLintAtLine(
         $line,
         0,
         self::LINT_MISSING_DEPENDENCY,
         "This file uses '{$class}' but does not @requires the component ".
         "which installs it. You may need to rebuild the Celerity map.");
     }
 
     foreach ($requires as $component) {
       $this->raiseLintAtLine(
         0,
         0,
         self::LINT_UNNECESSARY_DEPENDENCY,
         "This file @requires component '{$component}' but does not use ".
         "anything it provides.");
     }
   }
 
   private function loadSymbols($path) {
     if (empty($this->symbols[$path])) {
       $this->symbols[$path] = $this->newSymbolsFuture($path)->resolvex();
     }
     return $this->symbols[$path];
   }
 
   private function newSymbolsFuture($path) {
     $future = new ExecFuture('javelinsymbols # %s', $path);
     $future->write($this->getData($path));
     return $future;
   }
 
   private function getUsedAndInstalledSymbolsForPath($path) {
     list($symbols) = $this->loadSymbols($path);
     $symbols = trim($symbols);
 
     $uses = array();
     $installs = array();
     if (empty($symbols)) {
       // This file has no symbols.
       return array($uses, $installs);
     }
 
     $symbols = explode("\n", trim($symbols));
     foreach ($symbols as $line) {
       $matches = null;
       if (!preg_match('/^([?+\*])([^:]*):(\d+)$/', $line, $matches)) {
         throw new Exception(
           'Received malformed output from `javelinsymbols`.');
       }
       $type = $matches[1];
       $symbol = $matches[2];
       $line = $matches[3];
 
       switch ($type) {
         case '?':
           $uses[$symbol] = $line;
           break;
         case '+':
           $installs['JX.'.$symbol] = $line;
           break;
       }
     }
 
     $contents = $this->getData($path);
 
     $matches = null;
     $count = preg_match_all(
       '/@javelin-installs\W+(\S+)/',
       $contents,
       $matches,
       PREG_PATTERN_ORDER);
 
     if ($count) {
       foreach ($matches[1] as $symbol) {
         $installs[$symbol] = 0;
       }
     }
 
     return array($uses, $installs);
   }
 
 }