(stable) Promote 2019 Week 39

resources/celerity/map.php

@@ -9,10 +9,10 @@ return array(
   'names' => array(
     'conpherence.pkg.css' => '3c8a0668',
     'conpherence.pkg.js' => '020aebcf',
-    'core.pkg.css' => 'c69171e6',
+    'core.pkg.css' => '7ce5a944',
-    'core.pkg.js' => '73a06a9f',
+    'core.pkg.js' => '6e5c894f',
-    'differential.pkg.css' => '8d8360fb',
+    'differential.pkg.css' => '607c84be',
-    'differential.pkg.js' => '0b037a4f',
+    'differential.pkg.js' => 'a0212a0b',
     'diffusion.pkg.css' => '42c75c37',
     'diffusion.pkg.js' => 'a98c0bf7',
     'maniphest.pkg.css' => '35995d6d',
@@ -61,7 +61,7 @@ return array(
     'rsrc/css/application/dashboard/dashboard.css' => '5a205b9d',
     'rsrc/css/application/diff/inline-comment-summary.css' => '81eb368d',
     'rsrc/css/application/differential/add-comment.css' => '7e5900d9',
-    'rsrc/css/application/differential/changeset-view.css' => 'bde53589',
+    'rsrc/css/application/differential/changeset-view.css' => '489b6995',
     'rsrc/css/application/differential/core.css' => '7300a73e',
     'rsrc/css/application/differential/phui-inline-comment.css' => '48acce5b',
     'rsrc/css/application/differential/revision-comment.css' => '7dbc8d1d',
@@ -113,7 +113,7 @@ return array(
     'rsrc/css/application/uiexample/example.css' => 'b4795059',
     'rsrc/css/core/core.css' => '1b29ed61',
     'rsrc/css/core/remarkup.css' => 'f06cc20e',
-    'rsrc/css/core/syntax.css' => '4234f572',
+    'rsrc/css/core/syntax.css' => '220b85f9',
     'rsrc/css/core/z-index.css' => '99c0f5eb',
     'rsrc/css/diviner/diviner-shared.css' => '4bd263b0',
     'rsrc/css/font/font-awesome.css' => '3883938a',
@@ -169,7 +169,7 @@ return array(
     'rsrc/css/phui/phui-pager.css' => 'd022c7ad',
     'rsrc/css/phui/phui-pinboard-view.css' => '1f08f5d8',
     'rsrc/css/phui/phui-policy-section-view.css' => '139fdc64',
-    'rsrc/css/phui/phui-property-list-view.css' => 'cad62236',
+    'rsrc/css/phui/phui-property-list-view.css' => '807b1632',
     'rsrc/css/phui/phui-remarkup-preview.css' => '91767007',
     'rsrc/css/phui/phui-segment-bar-view.css' => '5166b370',
     'rsrc/css/phui/phui-spacing.css' => 'b05cadc3',
@@ -376,8 +376,8 @@ return array(
     'rsrc/js/application/dashboard/behavior-dashboard-move-panels.js' => 'a2ab19be',
     'rsrc/js/application/dashboard/behavior-dashboard-query-panel-select.js' => '1e413dc9',
     'rsrc/js/application/dashboard/behavior-dashboard-tab-panel.js' => '0116d3e8',
-    'rsrc/js/application/diff/DiffChangeset.js' => 'd0a85a85',
+    'rsrc/js/application/diff/DiffChangeset.js' => 'a31ffc00',
-    'rsrc/js/application/diff/DiffChangesetList.js' => '04023d82',
+    'rsrc/js/application/diff/DiffChangesetList.js' => '0f5c016d',
     'rsrc/js/application/diff/DiffInline.js' => 'a4a14a94',
     'rsrc/js/application/diff/behavior-preview-link.js' => 'f51e9c17',
     'rsrc/js/application/differential/behavior-diff-radios.js' => '925fe8cd',
@@ -506,7 +506,7 @@ return array(
     'rsrc/js/core/behavior-tokenizer.js' => '3b4899b0',
     'rsrc/js/core/behavior-tooltip.js' => '73ecc1f8',
     'rsrc/js/core/behavior-user-menu.js' => '60cd9241',
-    'rsrc/js/core/behavior-watch-anchor.js' => '0e6d261f',
+    'rsrc/js/core/behavior-watch-anchor.js' => '3972dadb',
     'rsrc/js/core/behavior-workflow.js' => '9623adc1',
     'rsrc/js/core/darkconsole/DarkLog.js' => '3b869402',
     'rsrc/js/core/darkconsole/DarkMessage.js' => '26cd4b73',
@@ -554,7 +554,7 @@ return array(
     'conpherence-thread-manager' => 'aec8e38c',
     'conpherence-transaction-css' => '3a3f5e7e',
     'd3' => '9d068042',
-    'differential-changeset-view-css' => 'bde53589',
+    'differential-changeset-view-css' => '489b6995',
     'differential-core-view-css' => '7300a73e',
     'differential-revision-add-comment-css' => '7e5900d9',
     'differential-revision-comment-css' => '7dbc8d1d',
@@ -655,7 +655,7 @@ return array(
     'javelin-behavior-phabricator-tooltips' => '73ecc1f8',
     'javelin-behavior-phabricator-transaction-comment-form' => '2bdadf1a',
     'javelin-behavior-phabricator-transaction-list' => '9cec214e',
-    'javelin-behavior-phabricator-watch-anchor' => '0e6d261f',
+    'javelin-behavior-phabricator-watch-anchor' => '3972dadb',
     'javelin-behavior-pholio-mock-edit' => '3eed1f2b',
     'javelin-behavior-pholio-mock-view' => '5aa1544e',
     'javelin-behavior-phui-dropdown-menu' => '5cf0501a',
@@ -773,8 +773,8 @@ return array(
     'phabricator-darklog' => '3b869402',
     'phabricator-darkmessage' => '26cd4b73',
     'phabricator-dashboard-css' => '5a205b9d',
-    'phabricator-diff-changeset' => 'd0a85a85',
+    'phabricator-diff-changeset' => 'a31ffc00',
-    'phabricator-diff-changeset-list' => '04023d82',
+    'phabricator-diff-changeset-list' => '0f5c016d',
     'phabricator-diff-inline' => 'a4a14a94',
     'phabricator-drag-and-drop-file-upload' => '4370900d',
     'phabricator-draggable-list' => 'c9ad6f70',
@@ -865,7 +865,7 @@ return array(
     'phui-pager-css' => 'd022c7ad',
     'phui-pinboard-view-css' => '1f08f5d8',
     'phui-policy-section-view-css' => '139fdc64',
-    'phui-property-list-view-css' => 'cad62236',
+    'phui-property-list-view-css' => '807b1632',
     'phui-remarkup-preview-css' => '91767007',
     'phui-segment-bar-view-css' => '5166b370',
     'phui-spacing-css' => 'b05cadc3',
@@ -900,7 +900,7 @@ return array(
     'sprite-login-css' => '18b368a6',
     'sprite-tokens-css' => 'f1896dc5',
     'syntax-default-css' => '055fc231',
-    'syntax-highlighting-css' => '4234f572',
+    'syntax-highlighting-css' => '220b85f9',
     'tokens-css' => 'ce5a50bd',
     'trigger-rule' => '41b7b4f6',
     'trigger-rule-control' => '5faf27b9',
@@ -944,10 +944,6 @@ return array(
     '03e8891f' => array(
       'javelin-install',
     ),
-    '04023d82' => array(
-      'javelin-install',
-      'phuix-button-view',
-    ),
     '04f8a1e3' => array(
       'javelin-behavior',
       'javelin-stratcom',
@@ -999,12 +995,6 @@ return array(
     '0d2490ce' => array(
       'javelin-install',
     ),
-    '0e6d261f' => array(
-      'javelin-behavior',
-      'javelin-stratcom',
-      'javelin-dom',
-      'javelin-vector',
-    ),
     '0eaa33a9' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1015,6 +1005,10 @@ return array(
       'javelin-workflow',
       'phuix-icon-view',
     ),
+    '0f5c016d' => array(
+      'javelin-install',
+      'phuix-button-view',
+    ),
     '111bfd2d' => array(
       'javelin-install',
     ),
@@ -1075,6 +1069,9 @@ return array(
       'javelin-behavior',
       'javelin-request',
     ),
+    '220b85f9' => array(
+      'syntax-default-css',
+    ),
     '225bbb98' => array(
       'javelin-install',
       'javelin-reactor',
@@ -1227,6 +1224,12 @@ return array(
       'javelin-install',
       'javelin-dom',
     ),
+    '3972dadb' => array(
+      'javelin-behavior',
+      'javelin-stratcom',
+      'javelin-dom',
+      'javelin-vector',
+    ),
     '398fdf13' => array(
       'javelin-behavior',
       'trigger-rule-editor',
@@ -1260,9 +1263,6 @@ return array(
       'javelin-behavior',
       'javelin-uri',
     ),
-    '4234f572' => array(
-      'syntax-default-css',
-    ),
     '4370900d' => array(
       'javelin-install',
       'javelin-util',
@@ -1303,6 +1303,9 @@ return array(
       'javelin-dom',
       'phabricator-draggable-list',
     ),
+    '489b6995' => array(
+      'phui-inline-comment-view-css',
+    ),
     '48fe33d0' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -1785,6 +1788,17 @@ return array(
       'javelin-workflow',
       'phabricator-draggable-list',
     ),
+    'a31ffc00' => array(
+      'javelin-dom',
+      'javelin-util',
+      'javelin-stratcom',
+      'javelin-install',
+      'javelin-workflow',
+      'javelin-router',
+      'javelin-behavior-device',
+      'javelin-vector',
+      'phabricator-diff-inline',
+    ),
     'a4356cde' => array(
       'javelin-install',
       'javelin-dom',
@@ -1960,9 +1974,6 @@ return array(
       'phabricator-drag-and-drop-file-upload',
       'javelin-workboard-board',
     ),
-    'bde53589' => array(
-      'phui-inline-comment-view-css',
-    ),
     'c03f2fb4' => array(
       'javelin-install',
     ),
@@ -2034,17 +2045,6 @@ return array(
       'javelin-dom',
       'javelin-stratcom',
     ),
-    'd0a85a85' => array(
-      'javelin-dom',
-      'javelin-util',
-      'javelin-stratcom',
-      'javelin-install',
-      'javelin-workflow',
-      'javelin-router',
-      'javelin-behavior-device',
-      'javelin-vector',
-      'phabricator-diff-inline',
-    ),
     'd12d214f' => array(
       'javelin-install',
       'javelin-dom',

resources/sql/autopatches/20190924.diffusion.01.permanent.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_repository.repository_refcursor
+  ADD isPermanent BOOL NOT NULL;

resources/sql/autopatches/20190924.diffusion.02.default.sql

@@ -0,0 +1,2 @@
+UPDATE {$NAMESPACE}_repository.repository_refcursor
+  SET isPermanent = 1;

src/__phutil_library_map__.php

@@ -2150,6 +2150,7 @@ phutil_register_library_map(array(
     'PhabricatorAlmanacApplication' => 'applications/almanac/application/PhabricatorAlmanacApplication.php',
     'PhabricatorAmazonAuthProvider' => 'applications/auth/provider/PhabricatorAmazonAuthProvider.php',
     'PhabricatorAmazonSNSFuture' => 'applications/metamta/future/PhabricatorAmazonSNSFuture.php',
+    'PhabricatorAnchorTestCase' => 'infrastructure/markup/__tests__/PhabricatorAnchorTestCase.php',
     'PhabricatorAnchorView' => 'view/layout/PhabricatorAnchorView.php',
     'PhabricatorAphlictManagementDebugWorkflow' => 'applications/aphlict/management/PhabricatorAphlictManagementDebugWorkflow.php',
     'PhabricatorAphlictManagementNotifyWorkflow' => 'applications/aphlict/management/PhabricatorAphlictManagementNotifyWorkflow.php',
@@ -2267,6 +2268,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthChallengeStatusController' => 'applications/auth/controller/mfa/PhabricatorAuthChallengeStatusController.php',
     'PhabricatorAuthChallengeUpdate' => 'applications/auth/view/PhabricatorAuthChallengeUpdate.php',
     'PhabricatorAuthChangePasswordAction' => 'applications/auth/action/PhabricatorAuthChangePasswordAction.php',
+    'PhabricatorAuthChangeUsernameMessageType' => 'applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php',
     'PhabricatorAuthConduitAPIMethod' => 'applications/auth/conduit/PhabricatorAuthConduitAPIMethod.php',
     'PhabricatorAuthConduitTokenRevoker' => 'applications/auth/revoker/PhabricatorAuthConduitTokenRevoker.php',
     'PhabricatorAuthConfirmLinkController' => 'applications/auth/controller/PhabricatorAuthConfirmLinkController.php',
@@ -3136,6 +3138,9 @@ phutil_register_library_map(array(
     'PhabricatorDividerProfileMenuItem' => 'applications/search/menuitem/PhabricatorDividerProfileMenuItem.php',
     'PhabricatorDivinerApplication' => 'applications/diviner/application/PhabricatorDivinerApplication.php',
     'PhabricatorDocumentEngine' => 'applications/files/document/PhabricatorDocumentEngine.php',
+    'PhabricatorDocumentEngineBlock' => 'applications/files/diff/PhabricatorDocumentEngineBlock.php',
+    'PhabricatorDocumentEngineBlockDiff' => 'applications/files/diff/PhabricatorDocumentEngineBlockDiff.php',
+    'PhabricatorDocumentEngineBlocks' => 'applications/files/diff/PhabricatorDocumentEngineBlocks.php',
     'PhabricatorDocumentRef' => 'applications/files/document/PhabricatorDocumentRef.php',
     'PhabricatorDocumentRenderingEngine' => 'applications/files/document/render/PhabricatorDocumentRenderingEngine.php',
     'PhabricatorDoorkeeperApplication' => 'applications/doorkeeper/application/PhabricatorDoorkeeperApplication.php',
@@ -4872,6 +4877,7 @@ phutil_register_library_map(array(
     'PhabricatorSystemRemoveWorkflow' => 'applications/system/management/PhabricatorSystemRemoveWorkflow.php',
     'PhabricatorSystemSelectEncodingController' => 'applications/system/controller/PhabricatorSystemSelectEncodingController.php',
     'PhabricatorSystemSelectHighlightController' => 'applications/system/controller/PhabricatorSystemSelectHighlightController.php',
+    'PhabricatorSystemSelectViewAsController' => 'applications/system/controller/PhabricatorSystemSelectViewAsController.php',
     'PhabricatorTOTPAuthFactor' => 'applications/auth/factor/PhabricatorTOTPAuthFactor.php',
     'PhabricatorTOTPAuthFactorTestCase' => 'applications/auth/factor/__tests__/PhabricatorTOTPAuthFactorTestCase.php',
     'PhabricatorTaskmasterDaemon' => 'infrastructure/daemon/workers/PhabricatorTaskmasterDaemon.php',
@@ -5594,9 +5600,13 @@ phutil_register_library_map(array(
     'PhutilOAuthAuthAdapter' => 'applications/auth/adapter/PhutilOAuthAuthAdapter.php',
     'PhutilPHPCodeSnippetContextFreeGrammar' => 'infrastructure/lipsum/code/PhutilPHPCodeSnippetContextFreeGrammar.php',
     'PhutilPhabricatorAuthAdapter' => 'applications/auth/adapter/PhutilPhabricatorAuthAdapter.php',
+    'PhutilProseDiff' => 'infrastructure/diff/prose/PhutilProseDiff.php',
+    'PhutilProseDiffTestCase' => 'infrastructure/diff/prose/__tests__/PhutilProseDiffTestCase.php',
+    'PhutilProseDifferenceEngine' => 'infrastructure/diff/prose/PhutilProseDifferenceEngine.php',
     'PhutilQsprintfInterface' => 'infrastructure/storage/xsprintf/PhutilQsprintfInterface.php',
     'PhutilQueryString' => 'infrastructure/storage/xsprintf/PhutilQueryString.php',
     'PhutilRealNameContextFreeGrammar' => 'infrastructure/lipsum/PhutilRealNameContextFreeGrammar.php',
+    'PhutilRemarkupAnchorRule' => 'infrastructure/markup/markuprule/PhutilRemarkupAnchorRule.php',
     'PhutilRemarkupBlockInterpreter' => 'infrastructure/markup/blockrule/PhutilRemarkupBlockInterpreter.php',
     'PhutilRemarkupBlockRule' => 'infrastructure/markup/blockrule/PhutilRemarkupBlockRule.php',
     'PhutilRemarkupBlockStorage' => 'infrastructure/markup/PhutilRemarkupBlockStorage.php',
@@ -8314,6 +8324,7 @@ phutil_register_library_map(array(
     'PhabricatorAlmanacApplication' => 'PhabricatorApplication',
     'PhabricatorAmazonAuthProvider' => 'PhabricatorOAuth2AuthProvider',
     'PhabricatorAmazonSNSFuture' => 'PhutilAWSFuture',
+    'PhabricatorAnchorTestCase' => 'PhabricatorTestCase',
     'PhabricatorAnchorView' => 'AphrontView',
     'PhabricatorAphlictManagementDebugWorkflow' => 'PhabricatorAphlictManagementWorkflow',
     'PhabricatorAphlictManagementNotifyWorkflow' => 'PhabricatorAphlictManagementWorkflow',
@@ -8452,6 +8463,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthChallengeStatusController' => 'PhabricatorAuthController',
     'PhabricatorAuthChallengeUpdate' => 'Phobject',
     'PhabricatorAuthChangePasswordAction' => 'PhabricatorSystemAction',
+    'PhabricatorAuthChangeUsernameMessageType' => 'PhabricatorAuthMessageType',
     'PhabricatorAuthConduitAPIMethod' => 'ConduitAPIMethod',
     'PhabricatorAuthConduitTokenRevoker' => 'PhabricatorAuthRevoker',
     'PhabricatorAuthConfirmLinkController' => 'PhabricatorAuthController',
@@ -9466,6 +9478,9 @@ phutil_register_library_map(array(
     'PhabricatorDividerProfileMenuItem' => 'PhabricatorProfileMenuItem',
     'PhabricatorDivinerApplication' => 'PhabricatorApplication',
     'PhabricatorDocumentEngine' => 'Phobject',
+    'PhabricatorDocumentEngineBlock' => 'Phobject',
+    'PhabricatorDocumentEngineBlockDiff' => 'Phobject',
+    'PhabricatorDocumentEngineBlocks' => 'Phobject',
     'PhabricatorDocumentRef' => 'Phobject',
     'PhabricatorDocumentRenderingEngine' => 'Phobject',
     'PhabricatorDoorkeeperApplication' => 'PhabricatorApplication',
@@ -11494,6 +11509,7 @@ phutil_register_library_map(array(
     'PhabricatorSystemRemoveWorkflow' => 'PhabricatorManagementWorkflow',
     'PhabricatorSystemSelectEncodingController' => 'PhabricatorController',
     'PhabricatorSystemSelectHighlightController' => 'PhabricatorController',
+    'PhabricatorSystemSelectViewAsController' => 'PhabricatorController',
     'PhabricatorTOTPAuthFactor' => 'PhabricatorAuthFactor',
     'PhabricatorTOTPAuthFactorTestCase' => 'PhabricatorTestCase',
     'PhabricatorTaskmasterDaemon' => 'PhabricatorDaemon',
@@ -12387,8 +12403,12 @@ phutil_register_library_map(array(
     'PhutilOAuthAuthAdapter' => 'PhutilAuthAdapter',
     'PhutilPHPCodeSnippetContextFreeGrammar' => 'PhutilCLikeCodeSnippetContextFreeGrammar',
     'PhutilPhabricatorAuthAdapter' => 'PhutilOAuthAuthAdapter',
+    'PhutilProseDiff' => 'Phobject',
+    'PhutilProseDiffTestCase' => 'PhabricatorTestCase',
+    'PhutilProseDifferenceEngine' => 'Phobject',
     'PhutilQueryString' => 'Phobject',
     'PhutilRealNameContextFreeGrammar' => 'PhutilContextFreeGrammar',
+    'PhutilRemarkupAnchorRule' => 'PhutilRemarkupRule',
     'PhutilRemarkupBlockInterpreter' => 'Phobject',
     'PhutilRemarkupBlockRule' => 'Phobject',
     'PhutilRemarkupBlockStorage' => 'Phobject',

src/aphront/response/Aphront403Response.php

@@ -28,7 +28,7 @@ final class Aphront403Response extends AphrontHTMLResponse {
     $dialog = id(new AphrontDialogView())
       ->setUser($user)
       ->setTitle(pht('403 Forbidden'))
-      ->addCancelButton('/', pht('Peace Out'))
+      ->addCancelButton('/', pht('Yikes!'))
       ->appendParagraph($forbidden_text);
 
     $view = id(new PhabricatorStandardPageView())

src/applications/auth/message/PhabricatorAuthChangeUsernameMessageType.php

@@ -0,0 +1,29 @@
+<?php
+
+final class PhabricatorAuthChangeUsernameMessageType
+  extends PhabricatorAuthMessageType {
+
+  const MESSAGEKEY = 'user.edit.username';
+
+  public function getDisplayName() {
+    return pht('Username Change Instructions');
+  }
+
+  public function getShortDescription() {
+    return pht(
+      'Guidance in the "Change Username" dialog for requesting a '.
+      'username change.');
+  }
+
+  public function getFullDescription() {
+    return pht(
+      'When users click the "Change Username" action on their profile pages '.
+      'but do not have the required permissions, they will be presented with '.
+      'a message explaining that they are not authorized to make the edit.'.
+      "\n\n".
+      'You can optionally provide additional instructions here to help users '.
+      'request a username change, if there is someone specific they should '.
+      'contact or a particular workflow they should use.');
+  }
+
+}

src/applications/conduit/query/PhabricatorConduitLogQuery.php

@@ -3,12 +3,18 @@
 final class PhabricatorConduitLogQuery
   extends PhabricatorCursorPagedPolicyAwareQuery {
 
+  private $ids;
   private $callerPHIDs;
   private $methods;
   private $methodStatuses;
   private $epochMin;
   private $epochMax;
 
+  public function withIDs(array $ids) {
+    $this->ids = $ids;
+    return $this;
+  }
+
   public function withCallerPHIDs(array $phids) {
     $this->callerPHIDs = $phids;
     return $this;
@@ -41,6 +47,13 @@ final class PhabricatorConduitLogQuery
   protected function buildWhereClauseParts(AphrontDatabaseConnection $conn) {
     $where = parent::buildWhereClauseParts($conn);
 
+    if ($this->ids !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'id IN (%Ld)',
+        $this->ids);
+    }
+
     if ($this->callerPHIDs !== null) {
       $where[] = qsprintf(
         $conn,

src/applications/differential/controller/DifferentialChangesetViewController.php

@@ -166,6 +166,7 @@ final class DifferentialChangesetViewController extends DifferentialController {
       DifferentialChangesetParser::parseRangeSpecification($spec);
 
     $parser = id(new DifferentialChangesetParser())
+      ->setViewer($viewer)
       ->setCoverage($coverage)
       ->setChangeset($changeset)
       ->setRenderingReference($rendering_reference)

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -58,6 +58,8 @@ final class DifferentialChangesetParser extends Phobject {
   private $linesOfContext = 8;
 
   private $highlightEngine;
+  private $viewer;
+  private $documentEngineKey;
 
   public function setRange($start, $end) {
     $this->rangeStart = $start;
@@ -149,6 +151,24 @@ final class DifferentialChangesetParser extends Phobject {
     return $this->offsetMode;
   }
 
+  public function setViewer(PhabricatorUser $viewer) {
+    $this->viewer = $viewer;
+    return $this;
+  }
+
+  public function getViewer() {
+    return $this->viewer;
+  }
+
+  public function setDocumentEngineKey($document_engine_key) {
+    $this->documentEngineKey = $document_engine_key;
+    return $this;
+  }
+
+  public function getDocumentEngineKey() {
+    return $this->documentEngineKey;
+  }
+
   public static function getDefaultRendererForViewer(PhabricatorUser $viewer) {
     $is_unified = $viewer->compareUserSetting(
       PhabricatorUnifiedDiffsSetting::SETTINGKEY,
@@ -164,6 +184,7 @@ final class DifferentialChangesetParser extends Phobject {
   public function readParametersFromRequest(AphrontRequest $request) {
     $this->setCharacterEncoding($request->getStr('encoding'));
     $this->setHighlightAs($request->getStr('highlight'));
+    $this->setDocumentEngineKey($request->getStr('engine'));
 
     $renderer = null;
 
@@ -226,7 +247,7 @@ final class DifferentialChangesetParser extends Phobject {
     return $this->depthOnlyLines;
   }
 
-  public function setVisibileLinesMask(array $mask) {
+  public function setVisibleLinesMask(array $mask) {
     $this->visible = $mask;
     return $this;
   }
@@ -678,13 +699,13 @@ final class DifferentialChangesetParser extends Phobject {
     $lines_context = $this->getLinesOfContext();
 
     $hunk_parser->generateIntraLineDiffs();
-    $hunk_parser->generateVisibileLinesMask($lines_context);
+    $hunk_parser->generateVisibleLinesMask($lines_context);
 
     $this->setOldLines($hunk_parser->getOldLines());
     $this->setNewLines($hunk_parser->getNewLines());
     $this->setIntraLineDiffs($hunk_parser->getIntraLineDiffs());
     $this->setDepthOnlyLines($hunk_parser->getDepthOnlyLines());
-    $this->setVisibileLinesMask($hunk_parser->getVisibleLinesMask());
+    $this->setVisibleLinesMask($hunk_parser->getVisibleLinesMask());
     $this->hunkStartLines = $hunk_parser->getHunkStartLines(
       $changeset->getHunks());
 
@@ -847,8 +868,19 @@ final class DifferentialChangesetParser extends Phobject {
       ->setHighlightingDisabled($this->highlightingDisabled)
       ->setDepthOnlyLines($this->getDepthOnlyLines());
 
+    list($engine, $old_ref, $new_ref) = $this->newDocumentEngine();
+    if ($engine) {
+      $engine_blocks = $engine->newEngineBlocks(
+        $old_ref,
+        $new_ref);
+    } else {
+      $engine_blocks = null;
+    }
+
+    $has_document_engine = ($engine_blocks !== null);
+
     $shield = null;
-    if ($this->isTopLevel && !$this->comments) {
+    if ($this->isTopLevel && !$this->comments && !$has_document_engine) {
       if ($this->isGenerated()) {
         $shield = $renderer->renderShield(
           pht(
@@ -1003,12 +1035,7 @@ final class DifferentialChangesetParser extends Phobject {
       ->setOldComments($old_comments)
       ->setNewComments($new_comments);
 
-    switch ($this->changeset->getFileType()) {
+    if ($engine_blocks !== null) {
-      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) {
@@ -1017,65 +1044,30 @@ final class DifferentialChangesetParser extends Phobject {
         $id = $parts[0];
         $vs = 0;
       }
-        $id = (int)$id;
-        $vs = (int)$vs;
 
+      // If we don't have an explicit "vs" changeset, it's the left side of
+      // the "id" changeset.
       if (!$vs) {
-          $metadata = $this->changeset->getMetadata();
+        $vs = $id;
-          $data = idx($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);
+      $renderer
-          if ($changeset) {
+        ->setDocumentEngine($engine)
-            $metadata = $changeset->getMetadata();
+        ->setDocumentEngineBlocks($engine_blocks);
-            $new_phid = idx($metadata, 'new:binary-phid');
+
-          }
+      return $renderer->renderDocumentEngineBlocks(
+        $engine_blocks,
+        (string)$id,
+        (string)$vs);
     }
 
-        if ($old_phid || $new_phid) {
+    // If we've made it here with a type of file we don't know how to render,
-          // grab the files, (micro) optimization for 1 query not 2
+    // bail out with a default empty rendering. Normally, we'd expect a
-          $file_phids = array();
+    // document engine to catch these changes before we make it this far.
-          if ($old_phid) {
+    switch ($this->changeset->getFileType()) {
-            $file_phids[] = $old_phid;
-          }
-          if ($new_phid) {
-            $file_phids[] = $new_phid;
-          }
-
-          $files = id(new PhabricatorFileQuery())
-            ->setViewer($this->getUser())
-            ->withPHIDs($file_phids)
-            ->execute();
-          foreach ($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:
+      case DifferentialChangeType::FILE_IMAGE:
         $output = $renderer->renderChangesetTable(null);
         return $output;
     }
@@ -1675,4 +1667,154 @@ final class DifferentialChangesetParser extends Phobject {
     return $prefix.$line;
   }
 
+  private function newDocumentEngine() {
+    $changeset = $this->changeset;
+    $viewer = $this->getViewer();
+
+    // TODO: This should probably be made non-optional in the future.
+    if (!$viewer) {
+      return null;
+    }
+
+    $old_file = null;
+    $new_file = null;
+
+    switch ($changeset->getFileType()) {
+      case DifferentialChangeType::FILE_IMAGE:
+      case DifferentialChangeType::FILE_BINARY:
+        list($old_file, $new_file) = $this->loadFileObjectsForChangeset();
+        break;
+    }
+
+    $old_ref = id(new PhabricatorDocumentRef())
+      ->setName($changeset->getOldFile());
+    if ($old_file) {
+      $old_ref->setFile($old_file);
+    } else {
+      $old_data = $this->old;
+      $old_data = ipull($old_data, 'text');
+      $old_data = implode('', $old_data);
+
+      $old_ref->setData($old_data);
+    }
+
+    $new_ref = id(new PhabricatorDocumentRef())
+      ->setName($changeset->getFilename());
+    if ($new_file) {
+      $new_ref->setFile($new_file);
+    } else {
+      $new_data = $this->new;
+      $new_data = ipull($new_data, 'text');
+      $new_data = implode('', $new_data);
+
+      $new_ref->setData($new_data);
+    }
+
+    $old_engines = PhabricatorDocumentEngine::getEnginesForRef(
+      $viewer,
+      $old_ref);
+
+    $new_engines = PhabricatorDocumentEngine::getEnginesForRef(
+      $viewer,
+      $new_ref);
+
+    $shared_engines = array_intersect_key($old_engines, $new_engines);
+
+    foreach ($shared_engines as $key => $shared_engine) {
+      if (!$shared_engine->canDiffDocuments($old_ref, $new_ref)) {
+        unset($shared_engines[$key]);
+      }
+    }
+
+    $engine_key = $this->getDocumentEngineKey();
+    if (strlen($engine_key)) {
+      if (isset($shared_engines[$engine_key])) {
+        $document_engine = $shared_engines[$engine_key];
+      } else {
+        $document_engine = null;
+      }
+    } else {
+      $document_engine = head($shared_engines);
+    }
+
+    if ($document_engine) {
+      return array(
+        $document_engine,
+        $old_ref,
+        $new_ref);
+    }
+
+    return null;
+  }
+
+  private function loadFileObjectsForChangeset() {
+    $changeset = $this->changeset;
+    $viewer = $this->getViewer();
+
+    $old_file = null;
+    $new_file = 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) {
+      $file_phids = array();
+      if ($old_phid) {
+        $file_phids[] = $old_phid;
+      }
+      if ($new_phid) {
+        $file_phids[] = $new_phid;
+      }
+
+      $files = id(new PhabricatorFileQuery())
+        ->setViewer($viewer)
+        ->withPHIDs($file_phids)
+        ->execute();
+
+      foreach ($files as $file) {
+        if ($file->getPHID() == $old_phid) {
+          $old_file = $file;
+        } else if ($file->getPHID() == $new_phid) {
+          $new_file = $file;
+        }
+      }
+    }
+
+    return array($old_file, $new_file);
+  }
+
 }

src/applications/differential/parser/DifferentialHunkParser.php

@@ -36,7 +36,7 @@ final class DifferentialHunkParser extends Phobject {
   }
   public function getVisibleLinesMask() {
     if ($this->visibleLinesMask === null) {
-      throw new PhutilInvalidStateException('generateVisibileLinesMask');
+      throw new PhutilInvalidStateException('generateVisibleLinesMask');
     }
     return $this->visibleLinesMask;
   }
@@ -354,7 +354,7 @@ final class DifferentialHunkParser extends Phobject {
     return $this;
   }
 
-  public function generateVisibileLinesMask($lines_context) {
+  public function generateVisibleLinesMask($lines_context) {
     $old = $this->getOldLines();
     $new = $this->getNewLines();
     $max_length = max(count($old), count($new));

src/applications/differential/render/DifferentialChangesetHTMLRenderer.php

@@ -270,11 +270,20 @@ abstract class DifferentialChangesetHTMLRenderer
       }
     }
 
+    $blocks = $this->getDocumentEngineBlocks();
+    if ($blocks) {
+      foreach ($blocks->getMessages() as $message) {
+        $messages[] = $message;
+      }
+    } else {
       if ($this->getHighlightingDisabled()) {
+        $byte_limit = DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT;
+        $byte_limit = phutil_format_bytes($byte_limit);
         $messages[] = pht(
           'This file is larger than %s, so syntax highlighting is '.
           'disabled by default.',
-        phutil_format_bytes(DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT));
+          $byte_limit);
+      }
     }
 
     return $this->formatHeaderMessages($messages);
@@ -608,17 +617,4 @@ abstract class DifferentialChangesetHTMLRenderer
     return array($left_prefix, $right_prefix);
   }
 
-  protected function renderImageStage(PhabricatorFile $file) {
-    return phutil_tag(
-      'div',
-      array(
-        'class' => 'differential-image-stage',
-      ),
-      phutil_tag(
-        'img',
-        array(
-          'src' => $file->getBestURI(),
-        )));
-  }
-
 }

src/applications/differential/render/DifferentialChangesetOneUpMailRenderer.php

@@ -31,14 +31,6 @@ final class DifferentialChangesetOneUpMailRenderer
     return null;
   }
 
-  public function renderFileChange(
-    $old_file = null,
-    $new_file = null,
-    $id = 0,
-    $vs = 0) {
-    return null;
-  }
-
   public function renderTextChange(
     $range_start,
     $range_len,

src/applications/differential/render/DifferentialChangesetOneUpRenderer.php

@@ -228,60 +228,238 @@ final class DifferentialChangesetOneUpRenderer
     return null;
   }
 
-  public function renderFileChange(
+  public function renderDocumentEngineBlocks(
-    $old_file = null,
+    PhabricatorDocumentEngineBlocks $block_list,
-    $new_file = null,
+    $old_changeset_key,
-    $id = 0,
+    $new_changeset_key) {
-    $vs = 0) {
 
-    // TODO: This should eventually merge into the normal primitives pathway,
+    $engine = $this->getDocumentEngine();
-    // but fake it for now and just share as much code as possible.
+    $layout = $block_list->newTwoUpLayout();
 
-    $primitives = array();
+    $old_comments = $this->getOldComments();
-    if ($old_file) {
+    $new_comments = $this->getNewComments();
-      $primitives[] = array(
+
-        'type' => 'old-file',
+    $unchanged = array();
-        'htype' => ($new_file ? 'new-file' : null),
+    foreach ($layout as $key => $row) {
-        'file' => $old_file,
+      list($old, $new) = $row;
-        'line' => 1,
+
-        'render' => $this->renderImageStage($old_file),
+      if (!$old) {
+        continue;
+      }
+
+      if (!$new) {
+        continue;
+      }
+
+      if ($old->getDifferenceType() !== null) {
+        continue;
+      }
+
+      if ($new->getDifferenceType() !== null) {
+        continue;
+      }
+
+      $unchanged[$key] = true;
+    }
+
+    $rows = array();
+    $count = count($layout);
+    for ($ii = 0; $ii < $count;) {
+      $start = $ii;
+
+      for ($jj = $ii; $jj < $count; $jj++) {
+        list($old, $new) = $layout[$jj];
+
+        if (empty($unchanged[$jj])) {
+          break;
+        }
+
+        $rows[] = array(
+          'type' => 'unchanged',
+          'layoutKey' => $jj,
+        );
+      }
+      $ii = $jj;
+
+      for ($jj = $ii; $jj < $count; $jj++) {
+        list($old, $new) = $layout[$jj];
+
+        if (!empty($unchanged[$jj])) {
+          break;
+        }
+
+        $rows[] = array(
+          'type' => 'old',
+          'layoutKey' => $jj,
         );
       }
 
-    if ($new_file) {
+      for ($jj = $ii; $jj < $count; $jj++) {
-      $primitives[] = array(
+        list($old, $new) = $layout[$jj];
-        'type' => 'new-file',
+
-        'htype' => ($old_file ? 'old-file' : null),
+        if (!empty($unchanged[$jj])) {
-        'file' => $new_file,
+          break;
-        'line' => 1,
-        'oline' => ($old_file ? 1 : null),
-        'render' => $this->renderImageStage($new_file),
-      );
         }
 
-    // TODO: We'd like to share primitive code here, but buildPrimitives()
+        $rows[] = array(
-    // currently chokes on changesets with no textual data.
+          'type' => 'new',
-    foreach ($this->getOldComments() as $line => $group) {
+          'layoutKey' => $jj,
-      foreach ($group as $comment) {
-        $primitives[] = array(
-          'type' => 'inline',
-          'comment' => $comment,
-          'right' => false,
         );
       }
+      $ii = $jj;
+
+      // We always expect to consume at least one row when iterating through
+      // the loop and make progress. If we don't, bail out to avoid spinning
+      // to death.
+      if ($ii === $start) {
+        throw new Exception(
+          pht(
+            'Failed to make progress during 1up diff layout.'));
+      }
     }
 
-    foreach ($this->getNewComments() as $line => $group) {
+    $old_ref = null;
-      foreach ($group as $comment) {
+    $new_ref = null;
-        $primitives[] = array(
+    $refs = $block_list->getDocumentRefs();
-          'type' => 'inline',
+    if ($refs) {
-          'comment' => $comment,
+      list($old_ref, $new_ref) = $refs;
-          'right' => true,
+    }
-        );
+
+    $view = array();
+    foreach ($rows as $row) {
+      $row_type = $row['type'];
+      $layout_key = $row['layoutKey'];
+      $row_layout = $layout[$layout_key];
+      list($old, $new) = $row_layout;
+
+      if ($old) {
+        $old_key = $old->getBlockKey();
+      } else {
+        $old_key = null;
+      }
+
+      if ($new) {
+        $new_key = $new->getBlockKey();
+      } else {
+        $new_key = null;
+      }
+
+      $cells = array();
+      $cell_classes = array();
+
+      if ($row_type === 'unchanged') {
+        $cell_content = $engine->newBlockContentView(
+          $old_ref,
+          $old);
+      } else if ($old && $new) {
+        $block_diff = $engine->newBlockDiffViews(
+          $old_ref,
+          $old,
+          $new_ref,
+          $new);
+
+        // TODO: We're currently double-rendering this: once when building
+        // the old row, and once when building the new one. In both cases,
+        // we throw away the other half of the output. We could cache this
+        // to improve performance.
+
+        if ($row_type === 'old') {
+          $cell_content = $block_diff->getOldContent();
+          $cell_classes = $block_diff->getOldClasses();
+        } else {
+          $cell_content = $block_diff->getNewContent();
+          $cell_classes = $block_diff->getNewClasses();
+        }
+      } else if ($row_type === 'old') {
+        $cell_content = $engine->newBlockContentView(
+          $old_ref,
+          $old);
+        $cell_classes[] = 'old';
+        $cell_classes[] = 'old-full';
+
+        $new_key = null;
+      } else if ($row_type === 'new') {
+        $cell_content = $engine->newBlockContentView(
+          $new_ref,
+          $new);
+        $cell_classes[] = 'new';
+        $cell_classes[] = 'new-full';
+
+        $old_key = null;
+      }
+
+      if ($old_key === null) {
+        $old_id = null;
+      } else {
+        $old_id = "C{$old_changeset_key}OL{$old_key}";
+      }
+
+      if ($new_key === null) {
+        $new_id = null;
+      } else {
+        $new_id = "C{$new_changeset_key}NL{$new_key}";
+      }
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'id' => $old_id,
+          'data-n' => $old_key,
+          'class' => 'n',
+        ));
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'id' => $new_id,
+          'data-n' => $new_key,
+          'class' => 'n',
+        ));
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'class' => 'copy',
+        ));
+
+      $cell_classes[] = 'diff-flush';
+      $cell_classes = implode(' ', $cell_classes);
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'class' => $cell_classes,
+          'data-copy-mode' => 'copy-unified',
+        ),
+        $cell_content);
+
+      $view[] = phutil_tag(
+        'tr',
+        array(),
+        $cells);
+
+      if ($old_key !== null) {
+        $old_inlines = idx($old_comments, $old_key, array());
+        foreach ($old_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = false);
+          $view[] = $this->getRowScaffoldForInline($inline);
         }
       }
 
-    $output = $this->renderPrimitives($primitives, 1);
+      if ($new_key !== null) {
+        $new_inlines = idx($new_comments, $new_key, array());
+        foreach ($new_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = true);
+          $view[] = $this->getRowScaffoldForInline($inline);
+        }
+      }
+    }
+
+    $output = $this->wrapChangeInTable($view);
     return $this->renderChangesetTable($output);
   }
 

src/applications/differential/render/DifferentialChangesetRenderer.php

@@ -36,6 +36,9 @@ abstract class DifferentialChangesetRenderer extends Phobject {
   private $scopeEngine = false;
   private $depthOnlyLines;
 
+  private $documentEngine;
+  private $documentEngineBlocks;
+
   private $oldFile = false;
   private $newFile = false;
 
@@ -239,6 +242,25 @@ abstract class DifferentialChangesetRenderer extends Phobject {
     return $this->oldChangesetID;
   }
 
+  public function setDocumentEngine(PhabricatorDocumentEngine $engine) {
+    $this->documentEngine = $engine;
+    return $this;
+  }
+
+  public function getDocumentEngine() {
+    return $this->documentEngine;
+  }
+
+  public function setDocumentEngineBlocks(
+    PhabricatorDocumentEngineBlocks $blocks) {
+    $this->documentEngineBlocks = $blocks;
+    return $this;
+  }
+
+  public function getDocumentEngineBlocks() {
+    return $this->documentEngineBlocks;
+  }
+
   public function setNewComments(array $new_comments) {
     foreach ($new_comments as $line_number => $comments) {
       assert_instances_of($comments, 'PhabricatorInlineCommentInterface');
@@ -355,6 +377,16 @@ abstract class DifferentialChangesetRenderer extends Phobject {
     $notice = null;
     if ($this->getIsTopLevel()) {
       $force = (!$content && !$props);
+
+      // If we have DocumentEngine messages about the blocks, assume they
+      // explain why there's no content.
+      $blocks = $this->getDocumentEngineBlocks();
+      if ($blocks) {
+        if ($blocks->getMessages()) {
+          $force = false;
+        }
+      }
+
       $notice = $this->renderChangeTypeHeader($force);
     }
 
@@ -378,11 +410,13 @@ abstract class DifferentialChangesetRenderer extends Phobject {
     $range_start,
     $range_len,
     $rows);
-  abstract public function renderFileChange(
+
-    $old = null,
+  public function renderDocumentEngineBlocks(
-    $new = null,
+    PhabricatorDocumentEngineBlocks $blocks,
-    $id = 0,
+    $old_changeset_key,
-    $vs = 0);
+    $new_changeset_key) {
+    return null;
+  }
 
   abstract protected function renderChangeTypeHeader($force);
   abstract protected function renderUndershieldHeader();

src/applications/differential/render/DifferentialChangesetTestRenderer.php

@@ -134,14 +134,4 @@ abstract class DifferentialChangesetTestRenderer
     return phutil_safe_html($out);
   }
 
-
-  public function renderFileChange(
-    $old_file = null,
-    $new_file = null,
-    $id = 0,
-    $vs = 0) {
-
-    throw new PhutilMethodNotImplementedException();
-  }
-
 }

src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php

@@ -364,76 +364,220 @@ final class DifferentialChangesetTwoUpRenderer
     return $this->wrapChangeInTable(phutil_implode_html('', $html));
   }
 
-  public function renderFileChange(
+  public function renderDocumentEngineBlocks(
-    $old_file = null,
+    PhabricatorDocumentEngineBlocks $block_list,
-    $new_file = null,
+    $old_changeset_key,
-    $id = 0,
+    $new_changeset_key) {
-    $vs = 0) {
 
-    $old = null;
+    $engine = $this->getDocumentEngine();
-    if ($old_file) {
+
-      $old = $this->renderImageStage($old_file);
+    $old_ref = null;
+    $new_ref = null;
+    $refs = $block_list->getDocumentRefs();
+    if ($refs) {
+      list($old_ref, $new_ref) = $refs;
     }
 
-    $new = null;
+    $old_comments = $this->getOldComments();
-    if ($new_file) {
+    $new_comments = $this->getNewComments();
-      $new = $this->renderImageStage($new_file);
-    }
 
-    // If we don't have an explicit "vs" changeset, it's the left side of the
+    $gap_view = javelin_tag(
-    // "id" changeset.
+      'tr',
-    if (!$vs) {
+      array(
-      $vs = $id;
+        'sigil' => 'context-target',
-    }
+      ),
+      phutil_tag(
+        'td',
+        array(
+          'colspan' => 6,
+          'class' => 'show-more',
+        ),
+        pht("\xE2\x80\xA2 \xE2\x80\xA2 \xE2\x80\xA2")));
 
-    $html_old = array();
+    $rows = array();
-    $html_new = array();
+    $in_gap = false;
-    foreach ($this->getOldComments() as $on_line => $comment_group) {
+    foreach ($block_list->newTwoUpLayout() as $row) {
-      foreach ($comment_group as $comment) {
+      list($old, $new) = $row;
-        $inline = $this->buildInlineComment(
-          $comment,
-          $on_right = false);
-        $html_old[] = $this->getRowScaffoldForInline($inline);
-      }
-    }
-    foreach ($this->getNewComments() as $lin_line => $comment_group) {
-      foreach ($comment_group as $comment) {
-        $inline = $this->buildInlineComment(
-          $comment,
-          $on_right = true);
-        $html_new[] = $this->getRowScaffoldForInline($inline);
-      }
-    }
 
-    if (!$old) {
+      if ($old) {
-      $th_old = phutil_tag('th', array());
+        $old_key = $old->getBlockKey();
+        $is_visible = $old->getIsVisible();
       } else {
-      $th_old = phutil_tag('th', array('id' => "C{$vs}OL1"), 1);
+        $old_key = null;
       }
 
-    if (!$new) {
+      if ($new) {
-      $th_new = phutil_tag('th', array());
+        $new_key = $new->getBlockKey();
+        $is_visible = $new->getIsVisible();
       } else {
-      $th_new = phutil_tag('th', array('id' => "C{$id}NL1"), 1);
+        $new_key = null;
       }
 
-    $output = hsprintf(
+      if (!$is_visible) {
-      '<tr class="differential-image-diff">'.
+        if (!$in_gap) {
-        '%s'.
+          $in_gap = true;
-        '<td class="differential-old-image">%s</td>'.
+          $rows[] = $gap_view;
-        '%s'.
+        }
-        '<td class="differential-new-image" colspan="3">%s</td>'.
+        continue;
-      '</tr>'.
+      }
-      '%s'.
+
-      '%s',
+      if ($in_gap) {
-      $th_old,
+        $in_gap = false;
+      }
+
+      if ($old) {
+        $is_rem = ($old->getDifferenceType() === '-');
+      } else {
+        $is_rem = false;
+      }
+
+      if ($new) {
+        $is_add = ($new->getDifferenceType() === '+');
+      } else {
+        $is_add = false;
+      }
+
+      if ($is_rem && $is_add) {
+        $block_diff = $engine->newBlockDiffViews(
+          $old_ref,
           $old,
-      $th_new,
+          $new_ref,
-      $new,
+          $new);
-      phutil_implode_html('', $html_old),
-      phutil_implode_html('', $html_new));
 
-    $output = $this->wrapChangeInTable($output);
+        $old_content = $block_diff->getOldContent();
+        $new_content = $block_diff->getNewContent();
+
+        $old_classes = $block_diff->getOldClasses();
+        $new_classes = $block_diff->getNewClasses();
+      } else {
+        $old_classes = array();
+        $new_classes = array();
+
+        if ($old) {
+          $old_content = $engine->newBlockContentView(
+            $old_ref,
+            $old);
+
+          if ($is_rem) {
+            $old_classes[] = 'old';
+            $old_classes[] = 'old-full';
+          }
+        } else {
+          $old_content = null;
+        }
+
+        if ($new) {
+          $new_content = $engine->newBlockContentView(
+            $new_ref,
+            $new);
+
+          if ($is_add) {
+            $new_classes[] = 'new';
+            $new_classes[] = 'new-full';
+          }
+        } else {
+          $new_content = null;
+        }
+      }
+
+      $old_classes[] = 'diff-flush';
+      $old_classes = implode(' ', $old_classes);
+
+      $new_classes[] = 'diff-flush';
+      $new_classes = implode(' ', $new_classes);
+
+      $old_inline_rows = array();
+      if ($old_key !== null) {
+        $old_inlines = idx($old_comments, $old_key, array());
+        foreach ($old_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = false);
+          $old_inline_rows[] = $this->getRowScaffoldForInline($inline);
+        }
+      }
+
+      $new_inline_rows = array();
+      if ($new_key !== null) {
+        $new_inlines = idx($new_comments, $new_key, array());
+        foreach ($new_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = true);
+          $new_inline_rows[] = $this->getRowScaffoldForInline($inline);
+        }
+      }
+
+      if ($old_content === null) {
+        $old_id = null;
+      } else {
+        $old_id = "C{$old_changeset_key}OL{$old_key}";
+      }
+
+      $old_line_cell = phutil_tag(
+        'td',
+        array(
+          'id' => $old_id,
+          'data-n' => $old_key,
+          'class' => 'n',
+        ));
+
+      $old_content_cell = phutil_tag(
+        'td',
+        array(
+          'class' => $old_classes,
+          'data-copy-mode' => 'copy-l',
+        ),
+        $old_content);
+
+      if ($new_content === null) {
+        $new_id = null;
+      } else {
+        $new_id = "C{$new_changeset_key}NL{$new_key}";
+      }
+
+      $new_line_cell = phutil_tag(
+        'td',
+        array(
+          'id' => $new_id,
+          'data-n' => $new_key,
+          'class' => 'n',
+        ));
+
+      $copy_gutter = phutil_tag(
+        'td',
+        array(
+          'class' => 'copy',
+        ));
+
+      $new_content_cell = phutil_tag(
+        'td',
+        array(
+          'class' => $new_classes,
+          'colspan' => '2',
+          'data-copy-mode' => 'copy-r',
+        ),
+        $new_content);
+
+      $row_view = phutil_tag(
+        'tr',
+        array(),
+        array(
+          $old_line_cell,
+          $old_content_cell,
+          $new_line_cell,
+          $copy_gutter,
+          $new_content_cell,
+        ));
+
+      $rows[] = array(
+        $row_view,
+        $old_inline_rows,
+        $new_inline_rows,
+      );
+    }
+
+    $output = $this->wrapChangeInTable($rows);
 
     return $this->renderChangesetTable($output);
   }

src/applications/differential/view/DifferentialChangesetListView.php

@@ -240,6 +240,7 @@ final class DifferentialChangesetListView extends AphrontView {
         'View Unified' => pht('View Unified'),
         'Change Text Encoding...' => pht('Change Text Encoding...'),
         'Highlight As...' => pht('Highlight As...'),
+        'View As...' => pht('View As...'),
 
         'Loading...' => pht('Loading...'),
 

src/applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php

@@ -195,13 +195,15 @@ final class DiffusionLowLevelResolveRefsQuery
 
       $alternate = null;
       if ($type == 'tag') {
+        $tag_identifier = idx($tag_map, $ref);
+        if ($tag_identifier === null) {
+          // This can happen when we're asked to resolve the hash of a "tag"
+          // object created with "git tag --annotate" that isn't currently
+          // reachable from any ref. Just leave things as they are.
+        } else {
+          // Otherwise, we have a normal named tag.
           $alternate = $identifier;
-        $identifier = idx($tag_map, $ref);
+          $identifier = $tag_identifier;
-        if (!$identifier) {
-          throw new Exception(
-            pht(
-              "Failed to look up tag '%s'!",
-              $ref));
         }
       }
 

src/applications/files/diff/PhabricatorDocumentEngineBlock.php

@@ -0,0 +1,57 @@
+<?php
+
+final class PhabricatorDocumentEngineBlock
+  extends Phobject {
+
+  private $blockKey;
+  private $content;
+  private $differenceHash;
+  private $differenceType;
+  private $isVisible;
+
+  public function setContent($content) {
+    $this->content = $content;
+    return $this;
+  }
+
+  public function getContent() {
+    return $this->content;
+  }
+
+  public function setBlockKey($block_key) {
+    $this->blockKey = $block_key;
+    return $this;
+  }
+
+  public function getBlockKey() {
+    return $this->blockKey;
+  }
+
+  public function setDifferenceHash($difference_hash) {
+    $this->differenceHash = $difference_hash;
+    return $this;
+  }
+
+  public function getDifferenceHash() {
+    return $this->differenceHash;
+  }
+
+  public function setDifferenceType($difference_type) {
+    $this->differenceType = $difference_type;
+    return $this;
+  }
+
+  public function getDifferenceType() {
+    return $this->differenceType;
+  }
+
+  public function setIsVisible($is_visible) {
+    $this->isVisible = $is_visible;
+    return $this;
+  }
+
+  public function getIsVisible() {
+    return $this->isVisible;
+  }
+
+}

src/applications/files/diff/PhabricatorDocumentEngineBlockDiff.php

@@ -0,0 +1,47 @@
+<?php
+
+final class PhabricatorDocumentEngineBlockDiff
+  extends Phobject {
+
+  private $oldContent;
+  private $newContent;
+  private $oldClasses = array();
+  private $newClasses = array();
+
+  public function setOldContent($old_content) {
+    $this->oldContent = $old_content;
+    return $this;
+  }
+
+  public function getOldContent() {
+    return $this->oldContent;
+  }
+
+  public function setNewContent($new_content) {
+    $this->newContent = $new_content;
+    return $this;
+  }
+
+  public function getNewContent() {
+    return $this->newContent;
+  }
+
+  public function addOldClass($class) {
+    $this->oldClasses[] = $class;
+    return $this;
+  }
+
+  public function getOldClasses() {
+    return $this->oldClasses;
+  }
+
+  public function addNewClass($class) {
+    $this->newClasses[] = $class;
+    return $this;
+  }
+
+  public function getNewClasses() {
+    return $this->newClasses;
+  }
+
+}

src/applications/files/diff/PhabricatorDocumentEngineBlocks.php

@@ -0,0 +1,179 @@
+<?php
+
+final class PhabricatorDocumentEngineBlocks
+  extends Phobject {
+
+  private $lists = array();
+  private $messages = array();
+
+  public function addMessage($message) {
+    $this->messages[] = $message;
+    return $this;
+  }
+
+  public function getMessages() {
+    return $this->messages;
+  }
+
+  public function addBlockList(PhabricatorDocumentRef $ref, array $blocks) {
+    assert_instances_of($blocks, 'PhabricatorDocumentEngineBlock');
+
+    $this->lists[] = array(
+      'ref' => $ref,
+      'blocks' => array_values($blocks),
+    );
+
+    return $this;
+  }
+
+  public function getDocumentRefs() {
+    return ipull($this->lists, 'ref');
+  }
+
+  public function newTwoUpLayout() {
+    $rows = array();
+    $lists = $this->lists;
+
+    if (count($lists) != 2) {
+      return array();
+    }
+
+    $specs = array();
+    foreach ($this->lists as $list) {
+      $specs[] = $this->newDiffSpec($list['blocks']);
+    }
+
+    $old_map = $specs[0]['map'];
+    $new_map = $specs[1]['map'];
+
+    $old_list = $specs[0]['list'];
+    $new_list = $specs[1]['list'];
+
+    $changeset = id(new PhabricatorDifferenceEngine())
+      ->generateChangesetFromFileContent($old_list, $new_list);
+
+    $hunk_parser = id(new DifferentialHunkParser())
+      ->parseHunksForLineData($changeset->getHunks())
+      ->reparseHunksForSpecialAttributes();
+
+    $hunk_parser->generateVisibleLinesMask(2);
+    $mask = $hunk_parser->getVisibleLinesMask();
+
+    $old_lines = $hunk_parser->getOldLines();
+    $new_lines = $hunk_parser->getNewLines();
+
+    $rows = array();
+
+    $count = count($old_lines);
+    for ($ii = 0; $ii < $count; $ii++) {
+      $old_line = idx($old_lines, $ii);
+      $new_line = idx($new_lines, $ii);
+
+      $is_visible = !empty($mask[$ii + 1]);
+
+      // TODO: There's currently a bug where one-line files get incorrectly
+      // masked. This causes images to completely fail to render. Just ignore
+      // the mask if it came back empty.
+      if (!$mask) {
+        $is_visible = true;
+      }
+
+      if ($old_line) {
+        $old_hash = rtrim($old_line['text'], "\n");
+        if (!strlen($old_hash)) {
+          // This can happen when one of the sources has no blocks.
+          $old_block = null;
+        } else {
+          $old_block = array_shift($old_map[$old_hash]);
+          $old_block
+            ->setDifferenceType($old_line['type'])
+            ->setIsVisible($is_visible);
+        }
+      } else {
+        $old_block = null;
+      }
+
+      if ($new_line) {
+        $new_hash = rtrim($new_line['text'], "\n");
+        if (!strlen($new_hash)) {
+          $new_block = null;
+        } else {
+          $new_block = array_shift($new_map[$new_hash]);
+          $new_block
+            ->setDifferenceType($new_line['type'])
+            ->setIsVisible($is_visible);
+        }
+      } else {
+        $new_block = null;
+      }
+
+      // If both lists are empty, we may generate a row which has two empty
+      // blocks.
+      if (!$old_block && !$new_block) {
+        continue;
+      }
+
+      $rows[] = array(
+        $old_block,
+        $new_block,
+      );
+    }
+
+    return $rows;
+  }
+
+  public function newOneUpLayout() {
+    $rows = array();
+    $lists = $this->lists;
+
+    $idx = 0;
+    while (true) {
+      $found_any = false;
+
+      $row = array();
+      foreach ($lists as $list) {
+        $blocks = $list['blocks'];
+        $cell = idx($blocks, $idx);
+
+        if ($cell !== null) {
+          $found_any = true;
+        }
+
+        if ($cell) {
+          $rows[] = $cell;
+        }
+      }
+
+      if (!$found_any) {
+        break;
+      }
+
+      $idx++;
+    }
+
+    return $rows;
+  }
+
+
+  private function newDiffSpec(array $blocks) {
+    $map = array();
+    $list = array();
+
+    foreach ($blocks as $block) {
+      $hash = $block->getDifferenceHash();
+
+      if (!isset($map[$hash])) {
+        $map[$hash] = array();
+      }
+      $map[$hash][] = $block;
+
+      $list[] = $hash;
+    }
+
+    return array(
+      'map' => $map,
+      'list' => implode("\n", $list)."\n",
+    );
+  }
+
+}

src/applications/files/document/PhabricatorDocumentEngine.php

@@ -31,6 +31,42 @@ abstract class PhabricatorDocumentEngine
     return $this->canRenderDocumentType($ref);
   }
 
+  public function canDiffDocuments(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+    return false;
+  }
+
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $u_content = $this->newBlockContentView($uref, $ublock);
+    $v_content = $this->newBlockContentView($vref, $vblock);
+
+    return id(new PhabricatorDocumentEngineBlockDiff())
+      ->setOldContent($u_content)
+      ->addOldClass('old')
+      ->addOldClass('old-full')
+      ->setNewContent($v_content)
+      ->addNewClass('new')
+      ->addNewClass('new-full');
+  }
+
+  public function newBlockContentView(
+    PhabricatorDocumentRef $ref,
+    PhabricatorDocumentEngineBlock $block) {
+    return $block->getContent();
+  }
+
+  public function newEngineBlocks(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+    throw new PhutilMethodNotImplementedException();
+  }
+
   public function canConfigureEncoding(PhabricatorDocumentRef $ref) {
     return false;
   }

src/applications/files/document/PhabricatorDocumentRef.php

@@ -11,6 +11,7 @@ final class PhabricatorDocumentRef
   private $symbolMetadata = array();
   private $blameURI;
   private $coverage = array();
+  private $data;
 
   public function setFile(PhabricatorFile $file) {
     $this->file = $file;
@@ -65,6 +66,10 @@ final class PhabricatorDocumentRef
       return $this->byteLength;
     }
 
+    if ($this->data !== null) {
+      return strlen($this->data);
+    }
+
     if ($this->file) {
       return (int)$this->file->getByteSize();
     }
@@ -72,7 +77,26 @@ final class PhabricatorDocumentRef
     return null;
   }
 
+  public function setData($data) {
+    $this->data = $data;
+    return $this;
+  }
+
   public function loadData($begin = null, $end = null) {
+    if ($this->data !== null) {
+      $data = $this->data;
+
+      if ($begin !== null && $end !== null) {
+        $data = substr($data, $begin, $end - $begin);
+      } else if ($begin !== null) {
+        $data = substr($data, $begin);
+      } else if ($end !== null) {
+        $data = substr($data, 0, $end);
+      }
+
+      return $data;
+    }
+
     if ($this->file) {
       $iterator = $this->file->getFileDataIterator($begin, $end);
 

src/applications/files/document/PhabricatorImageDocumentEngine.php

@@ -17,6 +17,71 @@ final class PhabricatorImageDocumentEngine
     return (1024 * 1024 * 64);
   }
 
+  public function canDiffDocuments(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+
+    // For now, we can only render a rich image diff if both documents have
+    // their data stored in Files already.
+
+    return ($uref->getFile() && $vref->getFile());
+  }
+
+  public function newEngineBlocks(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+
+    $u_blocks = $this->newDiffBlocks($uref);
+    $v_blocks = $this->newDiffBlocks($vref);
+
+    return id(new PhabricatorDocumentEngineBlocks())
+      ->addBlockList($uref, $u_blocks)
+      ->addBlockList($vref, $v_blocks);
+  }
+
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $u_content = $this->newBlockContentView($uref, $ublock);
+    $v_content = $this->newBlockContentView($vref, $vblock);
+
+    return id(new PhabricatorDocumentEngineBlockDiff())
+      ->setOldContent($u_content)
+      ->addOldClass('diff-image-cell')
+      ->setNewContent($v_content)
+      ->addNewClass('diff-image-cell');
+  }
+
+
+  private function newDiffBlocks(PhabricatorDocumentRef $ref) {
+    $blocks = array();
+
+    $file = $ref->getFile();
+
+    $image_view = phutil_tag(
+      'div',
+      array(
+        'class' => 'differential-image-stage',
+      ),
+      phutil_tag(
+        'img',
+        array(
+          'src' => $file->getBestURI(),
+        )));
+
+    $hash = $file->getContentHash();
+
+    $blocks[] = id(new PhabricatorDocumentEngineBlock())
+      ->setBlockKey('1')
+      ->setDifferenceHash($hash)
+      ->setContent($image_view);
+
+    return $blocks;
+  }
+
   protected function canRenderDocumentType(PhabricatorDocumentRef $ref) {
     $file = $ref->getFile();
     if ($file) {

src/applications/files/document/PhabricatorJupyterDocumentEngine.php

@@ -35,55 +35,198 @@ final class PhabricatorJupyterDocumentEngine
     return $ref->isProbablyJSON();
   }
 
+  public function canDiffDocuments(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+    return true;
+  }
+
+  public function newEngineBlocks(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentRef $vref) {
+
+    $blocks = new PhabricatorDocumentEngineBlocks();
+
+    try {
+      $u_blocks = $this->newDiffBlocks($uref);
+      $v_blocks = $this->newDiffBlocks($vref);
+
+      $blocks->addBlockList($uref, $u_blocks);
+      $blocks->addBlockList($vref, $v_blocks);
+    } catch (Exception $ex) {
+      $blocks->addMessage($ex->getMessage());
+    }
+
+    return $blocks;
+  }
+
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $ucell = $ublock->getContent();
+    $vcell = $vblock->getContent();
+
+    $utype = idx($ucell, 'cell_type');
+    $vtype = idx($vcell, 'cell_type');
+
+    if ($utype === $vtype) {
+      switch ($utype) {
+        case 'markdown':
+          $usource = idx($ucell, 'source');
+          $usource = implode('', $usource);
+
+          $vsource = idx($vcell, 'source');
+          $vsource = implode('', $vsource);
+
+          $diff = id(new PhutilProseDifferenceEngine())
+            ->getDiff($usource, $vsource);
+
+          $u_content = $this->newProseDiffCell($diff, array('=', '-'));
+          $v_content = $this->newProseDiffCell($diff, array('=', '+'));
+
+          $u_content = $this->newJupyterCell(null, $u_content, null);
+          $v_content = $this->newJupyterCell(null, $v_content, null);
+
+          $u_content = $this->newCellContainer($u_content);
+          $v_content = $this->newCellContainer($v_content);
+
+          return id(new PhabricatorDocumentEngineBlockDiff())
+            ->setOldContent($u_content)
+            ->addOldClass('old')
+            ->setNewContent($v_content)
+            ->addNewClass('new');
+      }
+    }
+
+    return parent::newBlockDiffViews($uref, $ublock, $vref, $vblock);
+  }
+
+  public function newBlockContentView(
+    PhabricatorDocumentRef $ref,
+    PhabricatorDocumentEngineBlock $block) {
+
+    $viewer = $this->getViewer();
+    $cell = $block->getContent();
+
+    $cell_content = $this->renderJupyterCell($viewer, $cell);
+
+    return $this->newCellContainer($cell_content);
+  }
+
+  private function newCellContainer($cell_content) {
+    $notebook_table = phutil_tag(
+      'table',
+      array(
+        'class' => 'jupyter-notebook',
+      ),
+      $cell_content);
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-jupyter document-engine-diff',
+      ),
+      $notebook_table);
+
+    return $container;
+  }
+
+  private function newProseDiffCell(PhutilProseDiff $diff, array $mask) {
+    $mask = array_fuse($mask);
+
+    $result = array();
+    foreach ($diff->getParts() as $part) {
+      $type = $part['type'];
+      $text = $part['text'];
+
+      if (!isset($mask[$type])) {
+        continue;
+      }
+
+      switch ($type) {
+        case '-':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'class' => 'bright',
+            ),
+            $text);
+          break;
+        case '+':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'class' => 'bright',
+            ),
+            $text);
+          break;
+        case '=':
+          $result[] = $text;
+          break;
+      }
+    }
+
+    return array(
+      null,
+      phutil_tag(
+        'div',
+        array(
+          'class' => 'jupyter-cell-markdown',
+        ),
+        $result),
+    );
+  }
+
+  private function newDiffBlocks(PhabricatorDocumentRef $ref) {
+    $viewer = $this->getViewer();
+    $content = $ref->loadData();
+
+    $cells = $this->newCells($content, true);
+
+    $idx = 1;
+    $blocks = array();
+    foreach ($cells as $cell) {
+      // When the cell is a source code line, we can hash just the raw
+      // input rather than all the cell metadata.
+
+      switch (idx($cell, 'cell_type')) {
+        case 'code/line':
+          $hash_input = $cell['raw'];
+          break;
+        case 'markdown':
+          $hash_input = implode('', $cell['source']);
+          break;
+        default:
+          $hash_input = serialize($cell);
+          break;
+      }
+
+      $hash = PhabricatorHash::digestWithNamedKey(
+        $hash_input,
+        'document-engine.content-digest');
+
+      $blocks[] = id(new PhabricatorDocumentEngineBlock())
+        ->setBlockKey($idx)
+        ->setDifferenceHash($hash)
+        ->setContent($cell);
+
+      $idx++;
+    }
+
+    return $blocks;
+  }
+
   protected function newDocumentContent(PhabricatorDocumentRef $ref) {
     $viewer = $this->getViewer();
     $content = $ref->loadData();
 
     try {
-      $data = phutil_json_decode($content);
+      $cells = $this->newCells($content, false);
-    } catch (PhutilJSONParserException $ex) {
+    } catch (Exception $ex) {
-      return $this->newMessage(
+      return $this->newMessage($ex->getMessage());
-        pht(
-          'This is not a valid JSON document and can not be rendered as '.
-          'a Jupyter notebook: %s.',
-          $ex->getMessage()));
-    }
-
-    if (!is_array($data)) {
-      return $this->newMessage(
-        pht(
-          'This document does not encode a valid JSON object and can not '.
-          'be rendered as a Jupyter notebook.'));
-    }
-
-
-    $nbformat = idx($data, 'nbformat');
-    if (!strlen($nbformat)) {
-      return $this->newMessage(
-        pht(
-          'This document is missing an "nbformat" field. Jupyter notebooks '.
-          'must have this field.'));
-    }
-
-    if ($nbformat !== 4) {
-      return $this->newMessage(
-        pht(
-          'This Jupyter notebook uses an unsupported version of the file '.
-          'format (found version %s, expected version 4).',
-          $nbformat));
-    }
-
-    $cells = idx($data, 'cells');
-    if (!is_array($cells)) {
-      return $this->newMessage(
-        pht(
-          'This Jupyter notebook does not specify a list of "cells".'));
-    }
-
-    if (!$cells) {
-      return $this->newMessage(
-        pht(
-          'This Jupyter notebook does not specify any notebook cells.'));
     }
 
     $rows = array();
@@ -108,20 +251,169 @@ final class PhabricatorJupyterDocumentEngine
     return $container;
   }
 
+  private function newCells($content, $for_diff) {
+    try {
+      $data = phutil_json_decode($content);
+    } catch (PhutilJSONParserException $ex) {
+      throw new Exception(
+        pht(
+          'This is not a valid JSON document and can not be rendered as '.
+          'a Jupyter notebook: %s.',
+          $ex->getMessage()));
+    }
+
+    if (!is_array($data)) {
+      throw new Exception(
+        pht(
+          'This document does not encode a valid JSON object and can not '.
+          'be rendered as a Jupyter notebook.'));
+    }
+
+
+    $nbformat = idx($data, 'nbformat');
+    if (!strlen($nbformat)) {
+      throw new Exception(
+        pht(
+          'This document is missing an "nbformat" field. Jupyter notebooks '.
+          'must have this field.'));
+    }
+
+    if ($nbformat !== 4) {
+      throw new Exception(
+        pht(
+          'This Jupyter notebook uses an unsupported version of the file '.
+          'format (found version %s, expected version 4).',
+          $nbformat));
+    }
+
+    $cells = idx($data, 'cells');
+    if (!is_array($cells)) {
+      throw new Exception(
+        pht(
+          'This Jupyter notebook does not specify a list of "cells".'));
+    }
+
+    if (!$cells) {
+      throw new Exception(
+        pht(
+          'This Jupyter notebook does not specify any notebook cells.'));
+    }
+
+    if (!$for_diff) {
+      return $cells;
+    }
+
+    // If we're extracting cells to build a diff view, split code cells into
+    // individual lines and individual outputs. We want users to be able to
+    // add inline comments to each line and each output block.
+
+    $results = array();
+    foreach ($cells as $cell) {
+      $cell_type = idx($cell, 'cell_type');
+
+      if ($cell_type === 'markdown') {
+        $source = $cell['source'];
+        $source = implode('', $source);
+
+        // Attempt to split contiguous blocks of markdown into smaller
+        // pieces.
+
+        $chunks = preg_split(
+          '/\n\n+/',
+          $source);
+
+        foreach ($chunks as $chunk) {
+          $result = $cell;
+          $result['source'] = array($chunk);
+          $results[] = $result;
+        }
+
+        continue;
+      }
+
+      if ($cell_type !== 'code') {
+        $results[] = $cell;
+        continue;
+      }
+
+      $label = $this->newCellLabel($cell);
+
+      $lines = idx($cell, 'source');
+      if (!is_array($lines)) {
+        $lines = array();
+      }
+
+      $content = $this->highlightLines($lines);
+
+      $count = count($lines);
+      for ($ii = 0; $ii < $count; $ii++) {
+        $is_head = ($ii === 0);
+        $is_last = ($ii === ($count - 1));
+
+        if ($is_head) {
+          $line_label = $label;
+        } else {
+          $line_label = null;
+        }
+
+        $results[] = array(
+          'cell_type' => 'code/line',
+          'label' => $line_label,
+          'raw' => $lines[$ii],
+          'display' => idx($content, $ii),
+          'head' => $is_head,
+          'last' => $is_last,
+        );
+      }
+
+      $outputs = array();
+      $output_list = idx($cell, 'outputs');
+      if (is_array($output_list)) {
+        foreach ($output_list as $output) {
+          $results[] = array(
+            'cell_type' => 'code/output',
+            'output' => $output,
+          );
+        }
+      }
+    }
+
+    return $results;
+  }
+
+
   private function renderJupyterCell(
     PhabricatorUser $viewer,
     array $cell) {
 
     list($label, $content) = $this->renderJupyterCellContent($viewer, $cell);
 
+    $classes = null;
+    switch (idx($cell, 'cell_type')) {
+      case 'code/line':
+        $classes = 'jupyter-cell-flush';
+        break;
+    }
+
+    return $this->newJupyterCell(
+      $label,
+      $content,
+      $classes);
+  }
+
+  private function newJupyterCell($label, $content, $classes) {
     $label_cell = phutil_tag(
-      'th',
+      'td',
-      array(),
+      array(
+        'class' => 'jupyter-label',
+      ),
       $label);
 
     $content_cell = phutil_tag(
       'td',
-      array(),
+      array(
+        'class' => $classes,
+      ),
       $content);
 
     return phutil_tag(
@@ -143,9 +435,14 @@ final class PhabricatorJupyterDocumentEngine
         return $this->newMarkdownCell($cell);
       case 'code':
         return $this->newCodeCell($cell);
+      case 'code/line':
+        return $this->newCodeLineCell($cell);
+      case 'code/output':
+        return $this->newCodeOutputCell($cell);
     }
 
-    return $this->newRawCell(id(new PhutilJSON())->encodeFormatted($cell));
+    return $this->newRawCell(id(new PhutilJSON())
+      ->encodeFormatted($cell));
   }
 
   private function newRawCell($content) {
@@ -166,8 +463,9 @@ final class PhabricatorJupyterDocumentEngine
       $content = array();
     }
 
-    $content = implode('', $content);
+    // TODO: This should ideally highlight as Markdown, but the "md"
-    $content = phutil_escape_html_newlines($content);
+    // highlighter in Pygments is painfully slow and not terribly useful.
+    $content = $this->highlightLines($content, 'txt');
 
     return array(
       null,
@@ -181,23 +479,14 @@ final class PhabricatorJupyterDocumentEngine
   }
 
   private function newCodeCell(array $cell) {
-    $execution_count = idx($cell, 'execution_count');
+    $label = $this->newCellLabel($cell);
-    if ($execution_count) {
-      $label = 'In ['.$execution_count.']:';
-    } else {
-      $label = null;
-    }
 
     $content = idx($cell, 'source');
     if (!is_array($content)) {
       $content = array();
     }
 
-    $content = implode('', $content);
+    $content = $this->highlightLines($content);
-
-    $content = PhabricatorSyntaxHighlighter::highlightWithLanguage(
-      'py',
-      $content);
 
     $outputs = array();
     $output_list = idx($cell, 'outputs');
@@ -213,7 +502,9 @@ final class PhabricatorJupyterDocumentEngine
         phutil_tag(
           'div',
           array(
-            'class' => 'jupyter-cell-code PhabricatorMonospaced remarkup-code',
+            'class' =>
+              'jupyter-cell-code jupyter-cell-code-block '.
+              'PhabricatorMonospaced remarkup-code',
           ),
           array(
             $content,
@@ -223,6 +514,45 @@ final class PhabricatorJupyterDocumentEngine
     );
   }
 
+  private function newCodeLineCell(array $cell) {
+    $classes = array();
+    $classes[] = 'PhabricatorMonospaced';
+    $classes[] = 'remarkup-code';
+    $classes[] = 'jupyter-cell-code';
+    $classes[] = 'jupyter-cell-code-line';
+
+    if ($cell['head']) {
+      $classes[] = 'jupyter-cell-code-head';
+    }
+
+    if ($cell['last']) {
+      $classes[] = 'jupyter-cell-code-last';
+    }
+
+    $classes = implode(' ', $classes);
+
+    return array(
+      $cell['label'],
+      array(
+        phutil_tag(
+          'div',
+          array(
+            'class' => $classes,
+          ),
+          array(
+            $cell['display'],
+          )),
+      ),
+    );
+  }
+
+  private function newCodeOutputCell(array $cell) {
+    return array(
+      null,
+      $this->newOutput($cell['output']),
+    );
+  }
+
   private function newOutput(array $output) {
     if (!is_array($output)) {
       return pht('<Invalid Output>');
@@ -309,4 +639,50 @@ final class PhabricatorJupyterDocumentEngine
       $content);
   }
 
+  private function newCellLabel(array $cell) {
+    $execution_count = idx($cell, 'execution_count');
+    if ($execution_count) {
+      $label = 'In ['.$execution_count.']:';
+    } else {
+      $label = null;
+    }
+
+    return $label;
+  }
+
+  private function highlightLines(array $lines, $force_language = null) {
+    if ($force_language === null) {
+      $head = head($lines);
+      $matches = null;
+      if (preg_match('/^%%(.*)$/', $head, $matches)) {
+        $restore = array_shift($lines);
+        $lang = $matches[1];
+      } else {
+        $restore = null;
+        $lang = 'py';
+      }
+    } else {
+      $restore = null;
+      $lang = $force_language;
+    }
+
+    $content = PhabricatorSyntaxHighlighter::highlightWithLanguage(
+      $lang,
+      implode('', $lines));
+    $content = phutil_split_lines($content);
+
+    if ($restore !== null) {
+      $language_tag = phutil_tag(
+        'span',
+        array(
+          'class' => 'language-tag',
+        ),
+        $restore);
+
+      array_unshift($content, $language_tag);
+    }
+
+    return $content;
+  }
+
 }

src/applications/people/controller/PhabricatorPeopleRenameController.php

@@ -3,8 +3,13 @@
 final class PhabricatorPeopleRenameController
   extends PhabricatorPeopleController {
 
+  public function shouldRequireAdmin() {
+    return false;
+  }
+
   public function handleRequest(AphrontRequest $request) {
     $viewer = $this->getViewer();
+
     $id = $request->getURIData('id');
 
     $user = id(new PhabricatorPeopleQuery())
@@ -17,6 +22,25 @@ final class PhabricatorPeopleRenameController
 
     $done_uri = $this->getApplicationURI("manage/{$id}/");
 
+    if (!$viewer->getIsAdmin()) {
+      $dialog = $this->newDialog()
+        ->setTitle(pht('Change Username'))
+        ->appendParagraph(
+          pht(
+            'You can not change usernames because you are not an '.
+            'administrator. Only administrators can change usernames.'))
+        ->addCancelButton($done_uri, pht('Okay'));
+
+      $message_body = PhabricatorAuthMessage::loadMessageText(
+        $viewer,
+        PhabricatorAuthChangeUsernameMessageType::MESSAGEKEY);
+      if (strlen($message_body)) {
+        $dialog->appendRemarkup($message_body);
+      }
+
+      return $dialog;
+    }
+
     $validation_exception = null;
     $username = $user->getUsername();
     if ($request->isFormOrHisecPost()) {
@@ -43,32 +67,25 @@ final class PhabricatorPeopleRenameController
 
     }
 
-    $inst1 = pht(
+    $instructions = array();
-      'Be careful when renaming users!');
 
-    $inst2 = pht(
+    $instructions[] = pht(
-      'The old username will no longer be tied to the user, so anything '.
+      'If you rename this user, the old username will no longer be tied '.
-      'which uses it (like old commit messages) will no longer associate '.
+      'to the user account. Anything which uses the old username in raw '.
-      'correctly. (And, if you give a user a username which some other user '.
+      'text (like old commit messages) may no longer associate correctly.');
-      'used to have, username lookups will begin returning the wrong user.)');
 
-    $inst3 = pht(
+    $instructions[] = pht(
-      'It is generally safe to rename newly created users (and test users '.
+      'It is generally safe to rename users, but changing usernames may '.
-      'and so on), but less safe to rename established users and unsafe to '.
+      'create occasional minor complications or confusion with text that '.
-      'reissue a username.');
+      'contains the old username.');
 
-    $inst4 = pht(
+    $instructions[] = pht(
-      'Users who rely on password authentication will need to reset their '.
-      'password after their username is changed (their username is part of '.
-      'the salt in the password hash).');
-
-    $inst5 = pht(
       'The user will receive an email notifying them that you changed their '.
-      'username, with instructions for logging in and resetting their '.
+      'username.');
-      'password if necessary.');
+
+    $instructions[] = null;
 
     $form = id(new AphrontFormView())
-      ->setUser($viewer)
       ->appendChild(
         id(new AphrontFormStaticControl())
           ->setLabel(pht('Old Username'))
@@ -79,19 +96,20 @@ final class PhabricatorPeopleRenameController
           ->setValue($username)
           ->setName('username'));
 
-    return $this->newDialog()
+    $dialog = $this->newDialog()
-      ->setWidth(AphrontDialogView::WIDTH_FORM)
       ->setTitle(pht('Change Username'))
-      ->setValidationException($validation_exception)
+      ->setValidationException($validation_exception);
-      ->appendParagraph($inst1)
+
-      ->appendParagraph($inst2)
+    foreach ($instructions as $instruction) {
-      ->appendParagraph($inst3)
+      $dialog->appendParagraph($instruction);
-      ->appendParagraph($inst4)
+    }
-      ->appendParagraph($inst5)
+
-      ->appendParagraph(null)
+    $dialog
       ->appendForm($form)
       ->addSubmitButton(pht('Rename User'))
       ->addCancelButton($done_uri);
+
+    return $dialog;
   }
 
 }

src/applications/repository/engine/PhabricatorRepositoryRefEngine.php

@@ -10,7 +10,16 @@ final class PhabricatorRepositoryRefEngine
   private $newPositions = array();
   private $deadPositions = array();
   private $closeCommits = array();
-  private $hasNoCursors;
+  private $rebuild;
+
+  public function setRebuild($rebuild) {
+    $this->rebuild = $rebuild;
+    return $this;
+  }
+
+  public function getRebuild() {
+    return $this->rebuild;
+  }
 
   public function updateRefs() {
     $this->newPositions = array();
@@ -60,15 +69,17 @@ final class PhabricatorRepositoryRefEngine
       ->execute();
     $cursor_groups = mgroup($all_cursors, 'getRefType');
 
-    $this->hasNoCursors = (!$all_cursors);
+    // Find all the heads of permanent refs.
-
-    // Find all the heads of closing refs.
     $all_closing_heads = array();
     foreach ($all_cursors as $cursor) {
-      $should_close = $this->shouldCloseRef(
+
-        $cursor->getRefType(),
+      // See T13284. Note that we're considering whether this ref was a
-        $cursor->getRefName());
+      // permanent ref or not the last time we updated refs for this
-      if (!$should_close) {
+      // repository. This allows us to handle things properly when a ref
+      // is reconfigured from non-permanent to permanent.
+
+      $was_permanent = $cursor->getIsPermanent();
+      if (!$was_permanent) {
         continue;
       }
 
@@ -76,6 +87,7 @@ final class PhabricatorRepositoryRefEngine
         $all_closing_heads[] = $identifier;
       }
     }
+
     $all_closing_heads = array_unique($all_closing_heads);
     $all_closing_heads = $this->removeMissingCommits($all_closing_heads);
 
@@ -88,12 +100,18 @@ final class PhabricatorRepositoryRefEngine
       $this->setCloseFlagOnCommits($this->closeCommits);
     }
 
-    if ($this->newPositions || $this->deadPositions) {
+    $save_cursors = $this->getCursorsForUpdate($all_cursors);
+
+    if ($this->newPositions || $this->deadPositions || $save_cursors) {
       $repository->openTransaction();
 
         $this->saveNewPositions();
         $this->deleteDeadPositions();
 
+        foreach ($save_cursors as $cursor) {
+          $cursor->save();
+        }
+
       $repository->saveTransaction();
     }
 
@@ -103,6 +121,28 @@ final class PhabricatorRepositoryRefEngine
     }
   }
 
+  private function getCursorsForUpdate(array $cursors) {
+    assert_instances_of($cursors, 'PhabricatorRepositoryRefCursor');
+
+    $results = array();
+
+    foreach ($cursors as $cursor) {
+      $ref_type = $cursor->getRefType();
+      $ref_name = $cursor->getRefName();
+
+      $is_permanent = $this->isPermanentRef($ref_type, $ref_name);
+
+      if ($is_permanent == $cursor->getIsPermanent()) {
+        continue;
+      }
+
+      $cursor->setIsPermanent((int)$is_permanent);
+      $results[] = $cursor;
+    }
+
+    return $results;
+  }
+
   private function updateBranchStates(
     PhabricatorRepository $repository,
     array $branches) {
@@ -301,11 +341,41 @@ final class PhabricatorRepositoryRefEngine
         $this->markPositionNew($new_position);
       }
 
-      if ($this->shouldCloseRef($ref_type, $name)) {
+      if ($this->isPermanentRef($ref_type, $name)) {
-        foreach ($added_commits as $identifier) {
+
+        // See T13284. If this cursor was already marked as permanent, we
+        // only need to publish the newly created ref positions. However, if
+        // this cursor was not previously permanent but has become permanent,
+        // we need to publish all the ref positions.
+
+        // This corresponds to users reconfiguring a branch to make it
+        // permanent without pushing any new commits to it.
+
+        $is_rebuild = $this->getRebuild();
+        $was_permanent = $ref_cursor->getIsPermanent();
+
+        if ($is_rebuild || !$was_permanent) {
+          $update_all = true;
+        } else {
+          $update_all = false;
+        }
+
+        if ($update_all) {
+          $update_commits = $new_commits;
+        } else {
+          $update_commits = $added_commits;
+        }
+
+        if ($is_rebuild) {
+          $exclude = array();
+        } else {
+          $exclude = $all_closing_heads;
+        }
+
+        foreach ($update_commits as $identifier) {
           $new_identifiers = $this->loadNewCommitIdentifiers(
             $identifier,
-            $all_closing_heads);
+            $exclude);
 
           $this->markCloseCommits($new_identifiers);
         }
@@ -334,19 +404,11 @@ final class PhabricatorRepositoryRefEngine
     }
   }
 
-  private function shouldCloseRef($ref_type, $ref_name) {
+  private function isPermanentRef($ref_type, $ref_name) {
     if ($ref_type !== PhabricatorRepositoryRefCursor::TYPE_BRANCH) {
       return false;
     }
 
-    if ($this->hasNoCursors) {
-      // If we don't have any cursors, don't close things. Particularly, this
-      // corresponds to the case where you've just updated to this code on an
-      // existing repository: we don't want to requeue message steps for every
-      // commit on a closeable ref.
-      return false;
-    }
-
     return $this->getRepository()->isBranchPermanentRef($ref_name);
   }
 
@@ -505,10 +567,13 @@ final class PhabricatorRepositoryRefEngine
     $ref_type,
     $ref_name) {
 
+    $is_permanent = $this->isPermanentRef($ref_type, $ref_name);
+
     $cursor = id(new PhabricatorRepositoryRefCursor())
       ->setRepositoryPHID($repository->getPHID())
       ->setRefType($ref_type)
-      ->setRefName($ref_name);
+      ->setRefName($ref_name)
+      ->setIsPermanent((int)$is_permanent);
 
     try {
       return $cursor->save();

src/applications/repository/management/PhabricatorRepositoryManagementRefsWorkflow.php

@@ -14,6 +14,12 @@ final class PhabricatorRepositoryManagementRefsWorkflow
             'name'        => 'verbose',
             'help'        => pht('Show additional debugging information.'),
           ),
+          array(
+            'name' => 'rebuild',
+            'help' => pht(
+              'Publish commits currently reachable from any permanent ref, '.
+              'ignoring the cached ref state.'),
+          ),
           array(
             'name'        => 'repos',
             'wildcard'    => true,
@@ -41,6 +47,7 @@ final class PhabricatorRepositoryManagementRefsWorkflow
       $engine = id(new PhabricatorRepositoryRefEngine())
         ->setRepository($repo)
         ->setVerbose($args->getArg('verbose'))
+        ->setRebuild($args->getArg('rebuild'))
         ->updateRefs();
     }
 

src/applications/repository/storage/PhabricatorRepositoryRefCursor.php

@@ -19,6 +19,7 @@ final class PhabricatorRepositoryRefCursor
   protected $refNameHash;
   protected $refNameRaw;
   protected $refNameEncoding;
+  protected $isPermanent;
 
   private $repository = self::ATTACHABLE;
   private $positions = self::ATTACHABLE;
@@ -34,6 +35,7 @@ final class PhabricatorRepositoryRefCursor
         'refType' => 'text32',
         'refNameHash' => 'bytes12',
         'refNameEncoding' => 'text16?',
+        'isPermanent' => 'bool',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_ref' => array(

src/applications/system/application/PhabricatorSystemApplication.php

@@ -22,6 +22,7 @@ final class PhabricatorSystemApplication extends PhabricatorApplication {
       '/services/' => array(
         'encoding/' => 'PhabricatorSystemSelectEncodingController',
         'highlight/' => 'PhabricatorSystemSelectHighlightController',
+        'viewas/' => 'PhabricatorSystemSelectViewAsController',
       ),
       '/readonly/' => array(
         '(?P<reason>[^/]+)/' => 'PhabricatorSystemReadOnlyController',

src/applications/system/controller/PhabricatorSystemSelectViewAsController.php

@@ -0,0 +1,63 @@
+<?php
+
+final class PhabricatorSystemSelectViewAsController
+  extends PhabricatorController {
+
+  public function shouldRequireLogin() {
+    return false;
+  }
+
+  public function handleRequest(AphrontRequest $request) {
+    $viewer = $this->getViewer();
+    $v_engine = $request->getStr('engine');
+
+    if ($request->isFormPost()) {
+      $result = array('engine' => $v_engine);
+      return id(new AphrontAjaxResponse())->setContent($result);
+    }
+
+    $engines = PhabricatorDocumentEngine::getAllEngines();
+
+
+    // TODO: This controller isn't very good because the valid options depend
+    // on the file being rendered and most of them can't even diff anything,
+    // and this ref is completely bogus.
+
+    // For now, we just show everything.
+    $ref = new PhabricatorDocumentRef();
+
+    $map = array();
+    foreach ($engines as $engine) {
+      $key = $engine->getDocumentEngineKey();
+      $label = $engine->getViewAsLabel($ref);
+
+      if (!strlen($label)) {
+        continue;
+      }
+
+      $map[$key] = $label;
+    }
+
+    asort($map);
+
+    $map = array(
+      '' => pht('(Use Default)'),
+    ) + $map;
+
+    $form = id(new AphrontFormView())
+      ->setViewer($viewer)
+      ->appendRemarkupInstructions(pht('Choose a document engine to use.'))
+      ->appendChild(
+        id(new AphrontFormSelectControl())
+          ->setLabel(pht('View As'))
+          ->setName('engine')
+          ->setValue($v_engine)
+          ->setOptions($map));
+
+    return $this->newDialog()
+      ->setTitle(pht('Select Document Engine'))
+      ->appendForm($form)
+      ->addSubmitButton(pht('Choose Engine'))
+      ->addCancelButton('/');
+  }
+}

src/applications/transactions/bulk/type/BulkTokenizerParameterType.php

@@ -22,7 +22,8 @@ final class BulkTokenizerParameterType
     $template = new AphrontTokenizerTemplateView();
     $template_markup = $template->render();
 
-    $datasource = $this->getDatasource();
+    $datasource = $this->getDatasource()
+      ->setViewer($this->getViewer());
 
     return array(
       'markup' => (string)hsprintf('%s', $template_markup),

src/applications/transactions/editengine/PhabricatorEditEngine.php

@@ -2523,6 +2523,8 @@ abstract class PhabricatorEditEngine
   }
 
   final public function newBulkEditMap() {
+    $viewer = $this->getViewer();
+
     $config = $this->loadDefaultConfiguration();
     if (!$config) {
       throw new Exception(
@@ -2542,6 +2544,8 @@ abstract class PhabricatorEditEngine
         continue;
       }
 
+      $bulk_type->setViewer($viewer);
+
       $bulk_label = $type->getBulkEditLabel();
       if ($bulk_label === null) {
         continue;

src/docs/user/userguide/remarkup.diviner

@@ -715,6 +715,18 @@ Press {key down down-right right LP} to activate the hadoken technique.
 > Press {key down down-right right LP} to activate the hadoken technique.
 
 
+Anchors
+========
+
+You can use `{anchor #xyz}` to create a document anchor and later link to
+it directly with `#xyz` in the URI.
+
+Headers also automatically create named anchors.
+
+If you navigate to `#xyz` in your browser location bar, the page will scroll
+to the first anchor with "xyz" as a prefix of the anchor name.
+
+
 = Fullscreen Mode =
 
 Remarkup editors provide a fullscreen composition mode. This can make it easier

src/infrastructure/diff/prose/PhutilProseDiff.php

@@ -0,0 +1,292 @@
+<?php
+
+final class PhutilProseDiff extends Phobject {
+
+  private $parts = array();
+
+  public function addPart($type, $text) {
+    $this->parts[] = array(
+      'type' => $type,
+      'text' => $text,
+    );
+    return $this;
+  }
+
+  public function getParts() {
+    return $this->parts;
+  }
+
+  /**
+   * Get diff parts, but replace large blocks of unchanged text with "."
+   * parts representing missing context.
+   */
+  public function getSummaryParts() {
+    $parts = $this->getParts();
+
+    $head_key = head_key($parts);
+    $last_key = last_key($parts);
+
+    $results = array();
+    foreach ($parts as $key => $part) {
+      $is_head = ($key == $head_key);
+      $is_last = ($key == $last_key);
+
+      switch ($part['type']) {
+        case '=':
+          $pieces = $this->splitTextForSummary($part['text']);
+
+          if ($is_head || $is_last) {
+            $need = 2;
+          } else {
+            $need = 3;
+          }
+
+          // We don't have enough pieces to omit anything, so just continue.
+          if (count($pieces) < $need) {
+            $results[] = $part;
+            break;
+          }
+
+          if (!$is_head) {
+            $results[] = array(
+              'type' => '=',
+              'text' => head($pieces),
+            );
+          }
+
+          $results[] = array(
+            'type' => '.',
+            'text' => null,
+          );
+
+          if (!$is_last) {
+            $results[] = array(
+              'type' => '=',
+              'text' => last($pieces),
+            );
+          }
+          break;
+        default:
+          $results[] = $part;
+          break;
+      }
+    }
+
+    return $results;
+  }
+
+
+  public function reorderParts() {
+    // Reorder sequences of removed and added sections to put all the "-"
+    // parts together first, then all the "+" parts together. This produces
+    // a more human-readable result than intermingling them.
+
+    $o_run = array();
+    $n_run = array();
+    $result = array();
+    foreach ($this->parts as $part) {
+      $type = $part['type'];
+      switch ($type) {
+        case '-':
+          $o_run[] = $part;
+          break;
+        case '+':
+          $n_run[] = $part;
+          break;
+        default:
+          if ($o_run || $n_run) {
+            foreach ($this->combineRuns($o_run, $n_run) as $merged_part) {
+              $result[] = $merged_part;
+            }
+            $o_run = array();
+            $n_run = array();
+          }
+          $result[] = $part;
+          break;
+      }
+    }
+
+    if ($o_run || $n_run) {
+      foreach ($this->combineRuns($o_run, $n_run) as $part) {
+        $result[] = $part;
+      }
+    }
+
+    // Now, combine consecuitive runs of the same type of change (like a
+    // series of "-" parts) into a single run.
+    $combined = array();
+
+    $last = null;
+    $last_text = null;
+    foreach ($result as $part) {
+      $type = $part['type'];
+
+      if ($last !== $type) {
+        if ($last !== null) {
+          $combined[] = array(
+            'type' => $last,
+            'text' => $last_text,
+          );
+        }
+        $last_text = null;
+        $last = $type;
+      }
+
+      $last_text .= $part['text'];
+    }
+
+    if ($last_text !== null) {
+      $combined[] = array(
+        'type' => $last,
+        'text' => $last_text,
+      );
+    }
+
+    $this->parts = $combined;
+
+    return $this;
+  }
+
+  private function combineRuns($o_run, $n_run) {
+    $o_merge = $this->mergeParts($o_run);
+    $n_merge = $this->mergeParts($n_run);
+
+    // When removed and added blocks share a prefix or suffix, we sometimes
+    // want to count it as unchanged (for example, if it is whitespace) but
+    // sometimes want to count it as changed (for example, if it is a word
+    // suffix like "ing"). Find common prefixes and suffixes of these layout
+    // characters and emit them as "=" (unchanged) blocks.
+
+    $layout_characters = array(
+      ' ' => true,
+      "\n" => true,
+      '.' => true,
+      '!' => true,
+      ',' => true,
+      '?' => true,
+      ']' => true,
+      '[' => true,
+      '(' => true,
+      ')' => true,
+      '<' => true,
+      '>' => true,
+    );
+
+    $o_text = $o_merge['text'];
+    $n_text = $n_merge['text'];
+    $o_len = strlen($o_text);
+    $n_len = strlen($n_text);
+    $min_len = min($o_len, $n_len);
+
+    $prefix_len = 0;
+    for ($pos = 0; $pos < $min_len; $pos++) {
+      $o = $o_text[$pos];
+      $n = $n_text[$pos];
+      if ($o !== $n) {
+        break;
+      }
+      if (empty($layout_characters[$o])) {
+        break;
+      }
+      $prefix_len++;
+    }
+
+    $suffix_len = 0;
+    for ($pos = 0; $pos < ($min_len - $prefix_len); $pos++) {
+      $o = $o_text[$o_len - ($pos + 1)];
+      $n = $n_text[$n_len - ($pos + 1)];
+      if ($o !== $n) {
+        break;
+      }
+      if (empty($layout_characters[$o])) {
+        break;
+      }
+      $suffix_len++;
+    }
+
+    $results = array();
+
+    if ($prefix_len) {
+      $results[] = array(
+        'type' => '=',
+        'text' => substr($o_text, 0, $prefix_len),
+      );
+    }
+
+    if ($prefix_len < $o_len) {
+      $results[] = array(
+        'type' => '-',
+        'text' => substr(
+          $o_text,
+          $prefix_len,
+          $o_len - $prefix_len - $suffix_len),
+      );
+    }
+
+    if ($prefix_len < $n_len) {
+      $results[] = array(
+        'type' => '+',
+        'text' => substr(
+          $n_text,
+          $prefix_len,
+          $n_len - $prefix_len - $suffix_len),
+      );
+    }
+
+    if ($suffix_len) {
+      $results[] = array(
+        'type' => '=',
+        'text' => substr($o_text, -$suffix_len),
+      );
+    }
+
+    return $results;
+  }
+
+  private function mergeParts(array $parts) {
+    $text = '';
+    $type = null;
+    foreach ($parts as $part) {
+      $part_type = $part['type'];
+      if ($type === null) {
+        $type = $part_type;
+      }
+      if ($type !== $part_type) {
+        throw new Exception(pht('Can not merge parts of dissimilar types!'));
+      }
+      $text .= $part['text'];
+    }
+
+    return array(
+      'type' => $type,
+      'text' => $text,
+    );
+  }
+
+  private function splitTextForSummary($text) {
+    $matches = null;
+
+    $ok = preg_match('/^(\n*[^\n]+)\n/', $text, $matches);
+    if (!$ok) {
+      return array($text);
+    }
+
+    $head = $matches[1];
+    $text = substr($text, strlen($head));
+
+    $ok = preg_match('/\n([^\n]+\n*)\z/', $text, $matches);
+    if (!$ok) {
+      return array($text);
+    }
+
+    $last = $matches[1];
+    $text = substr($text, 0, -strlen($last));
+
+    if (!strlen(trim($text))) {
+      return array($head, $last);
+    } else {
+      return array($head, $text, $last);
+    }
+  }
+
+}

src/infrastructure/diff/prose/PhutilProseDifferenceEngine.php

@@ -0,0 +1,275 @@
+<?php
+
+final class PhutilProseDifferenceEngine extends Phobject {
+
+  public function getDiff($u, $v) {
+    return $this->buildDiff($u, $v, 0);
+  }
+
+  private function buildDiff($u, $v, $level) {
+    $u_parts = $this->splitCorpus($u, $level);
+    $v_parts = $this->splitCorpus($v, $level);
+
+    if ($level === 0) {
+      $diff = $this->newHashDiff($u_parts, $v_parts);
+      $too_large = false;
+    } else {
+      list($diff, $too_large) = $this->newEditDistanceMatrixDiff(
+        $u_parts,
+        $v_parts,
+        $level);
+    }
+
+    $diff->reorderParts();
+
+    // If we just built a character-level diff, we're all done and do not
+    // need to go any deeper.
+    if ($level == 3) {
+      return $diff;
+    }
+
+    $blocks = array();
+    $block = null;
+    foreach ($diff->getParts() as $part) {
+      $type = $part['type'];
+      $text = $part['text'];
+      switch ($type) {
+        case '=':
+          if ($block) {
+            $blocks[] = $block;
+            $block = null;
+          }
+          $blocks[] = array(
+            'type' => $type,
+            'text' => $text,
+          );
+          break;
+        case '-':
+          if (!$block) {
+            $block = array(
+              'type' => '!',
+              'old' => '',
+              'new' => '',
+            );
+          }
+          $block['old'] .= $text;
+          break;
+        case '+':
+          if (!$block) {
+            $block = array(
+              'type' => '!',
+              'old' => '',
+              'new' => '',
+            );
+          }
+          $block['new'] .= $text;
+          break;
+      }
+    }
+
+    if ($block) {
+      $blocks[] = $block;
+    }
+
+    $result = new PhutilProseDiff();
+    foreach ($blocks as $block) {
+      $type = $block['type'];
+      if ($type == '=') {
+        $result->addPart('=', $block['text']);
+      } else {
+        $old = $block['old'];
+        $new = $block['new'];
+        if (!strlen($old) && !strlen($new)) {
+          // Nothing to do.
+        } else if (!strlen($old)) {
+          $result->addPart('+', $new);
+        } else if (!strlen($new)) {
+          $result->addPart('-', $old);
+        } else {
+          if ($too_large) {
+            // If this text was too big to diff, don't try to subdivide it.
+            $result->addPart('-', $old);
+            $result->addPart('+', $new);
+          } else {
+            $subdiff = $this->buildDiff(
+              $old,
+              $new,
+              $level + 1);
+
+            foreach ($subdiff->getParts() as $part) {
+              $result->addPart($part['type'], $part['text']);
+            }
+          }
+        }
+      }
+    }
+
+    $result->reorderParts();
+
+    return $result;
+  }
+
+  private function splitCorpus($corpus, $level) {
+    switch ($level) {
+      case 0:
+        // Level 0: Split into paragraphs.
+        $expr = '/([\n]+)/';
+        break;
+      case 1:
+        // Level 1: Split into sentences.
+        $expr = '/([\n,!;?\.]+)/';
+        break;
+      case 2:
+        // Level 2: Split into words.
+        $expr = '/(\s+)/';
+        break;
+      case 3:
+        // Level 3: Split into characters.
+        return phutil_utf8v_combined($corpus);
+    }
+
+    $pieces = preg_split($expr, $corpus, -1, PREG_SPLIT_DELIM_CAPTURE);
+    return $this->stitchPieces($pieces, $level);
+  }
+
+  private function stitchPieces(array $pieces, $level) {
+    $results = array();
+    $count = count($pieces);
+    for ($ii = 0; $ii < $count; $ii += 2) {
+      $result = $pieces[$ii];
+      if ($ii + 1 < $count) {
+        $result .= $pieces[$ii + 1];
+      }
+
+      if ($level < 2) {
+        // Split pieces into separate text and whitespace sections: make one
+        // piece out of all the whitespace at the beginning, one piece out of
+        // all the actual text in the middle, and one piece out of all the
+        // whitespace at the end.
+
+        $matches = null;
+        preg_match('/^(\s*)(.*?)(\s*)\z/', $result, $matches);
+
+        if (strlen($matches[1])) {
+          $results[] = $matches[1];
+        }
+        if (strlen($matches[2])) {
+          $results[] = $matches[2];
+        }
+        if (strlen($matches[3])) {
+          $results[] = $matches[3];
+        }
+      } else {
+        $results[] = $result;
+      }
+    }
+
+    // If the input ended with a delimiter, we can get an empty final piece.
+    // Just discard it.
+    if (last($results) == '') {
+      array_pop($results);
+    }
+
+    return $results;
+  }
+
+  private function newEditDistanceMatrixDiff(
+    array $u_parts,
+    array $v_parts,
+    $level) {
+
+    $matrix = id(new PhutilEditDistanceMatrix())
+      ->setMaximumLength(128)
+      ->setSequences($u_parts, $v_parts)
+      ->setComputeString(true);
+
+    // For word-level and character-level changes, smooth the output string
+    // to reduce the choppiness of the diff.
+    if ($level > 1) {
+      $matrix->setApplySmoothing(PhutilEditDistanceMatrix::SMOOTHING_FULL);
+    }
+
+    $u_pos = 0;
+    $v_pos = 0;
+
+    $edits = $matrix->getEditString();
+    $edits_length = strlen($edits);
+
+    $diff = new PhutilProseDiff();
+    for ($ii = 0; $ii < $edits_length; $ii++) {
+      $c = $edits[$ii];
+      if ($c == 's') {
+        $diff->addPart('=', $u_parts[$u_pos]);
+        $u_pos++;
+        $v_pos++;
+      } else if ($c == 'd') {
+        $diff->addPart('-', $u_parts[$u_pos]);
+        $u_pos++;
+      } else if ($c == 'i') {
+        $diff->addPart('+', $v_parts[$v_pos]);
+        $v_pos++;
+      } else if ($c == 'x') {
+        $diff->addPart('-', $u_parts[$u_pos]);
+        $diff->addPart('+', $v_parts[$v_pos]);
+        $u_pos++;
+        $v_pos++;
+      } else {
+        throw new Exception(
+          pht(
+            'Unexpected character ("%s") in edit string.',
+            $c));
+      }
+    }
+
+    return array($diff, $matrix->didReachMaximumLength());
+  }
+
+  private function newHashDiff(array $u_parts, array $v_parts) {
+
+    $u_ref = new PhabricatorDocumentRef();
+    $v_ref = new PhabricatorDocumentRef();
+
+    $u_blocks = $this->newDocumentEngineBlocks($u_parts);
+    $v_blocks = $this->newDocumentEngineBlocks($v_parts);
+
+    $rows = id(new PhabricatorDocumentEngineBlocks())
+      ->addBlockList($u_ref, $u_blocks)
+      ->addBlockList($v_ref, $v_blocks)
+      ->newTwoUpLayout();
+
+    $diff = new PhutilProseDiff();
+    foreach ($rows as $row) {
+      list($u_block, $v_block) = $row;
+
+      if ($u_block && $v_block) {
+        if ($u_block->getDifferenceType() === '-') {
+          $diff->addPart('-', $u_block->getContent());
+          $diff->addPart('+', $v_block->getContent());
+        } else {
+          $diff->addPart('=', $u_block->getContent());
+        }
+      } else if ($u_block) {
+        $diff->addPart('-', $u_block->getContent());
+      } else {
+        $diff->addPart('+', $v_block->getContent());
+      }
+    }
+
+    return $diff;
+  }
+
+  private function newDocumentEngineBlocks(array $parts) {
+    $blocks = array();
+
+    foreach ($parts as $part) {
+      $hash = PhabricatorHash::digestForIndex($part);
+
+      $blocks[] = id(new PhabricatorDocumentEngineBlock())
+        ->setContent($part)
+        ->setDifferenceHash($hash);
+    }
+
+    return $blocks;
+  }
+
+}

src/infrastructure/diff/prose/__tests__/PhutilProseDiffTestCase.php

@@ -0,0 +1,246 @@
+<?php
+
+final class PhutilProseDiffTestCase
+  extends PhabricatorTestCase {
+
+  public function testProseDiffsDistance() {
+    $this->assertProseParts(
+      '',
+      '',
+      array(),
+      pht('Empty'));
+
+    $this->assertProseParts(
+      "xxx\nyyy",
+      "xxx\nzzz\nyyy",
+      array(
+        "= xxx\n",
+        "+ zzz\n",
+        '= yyy',
+      ),
+      pht('Add Paragraph'));
+
+    $this->assertProseParts(
+      "xxx\nzzz\nyyy",
+      "xxx\nyyy",
+      array(
+        "= xxx\n",
+        "- zzz\n",
+        '= yyy',
+      ),
+      pht('Remove Paragraph'));
+
+
+    // Without smoothing, the alogorithm identifies that "shark" and "cat"
+    // both contain the letter "a" and tries to express this as a very
+    // fine-grained edit which replaces "sh" with "c" and then "rk" with "t".
+    // This is technically correct, but it is much easier for human viewers to
+    // parse if we smooth this into a single removal and a single addition.
+
+    $this->assertProseParts(
+      'They say the shark has nine lives.',
+      'They say the cat has nine lives.',
+      array(
+        '= They say the ',
+        '- shark',
+        '+ cat',
+        '=  has nine lives.',
+      ),
+      pht('"Shark/cat" word edit smoothenss.'));
+
+    $this->assertProseParts(
+      'Rising quickly, she says',
+      'Rising quickly, she remarks:',
+      array(
+        '= Rising quickly, she ',
+        '- says',
+        '+ remarks:',
+      ),
+      pht('"Says/remarks" word edit smoothenss.'));
+
+    $this->assertProseParts(
+      'See screenshots',
+      'Viewed video files',
+      array(
+        '- See screenshots',
+        '+ Viewed video files',
+      ),
+      pht('Complete paragraph rewrite.'));
+
+    $this->assertProseParts(
+      'xaaax',
+      'xbbbx',
+      array(
+        '- xaaax',
+        '+ xbbbx',
+      ),
+      pht('Whole word rewrite with common prefix and suffix.'));
+
+    $this->assertProseParts(
+      ' aaa ',
+      ' bbb ',
+      array(
+        '=  ',
+        '- aaa',
+        '+ bbb',
+        '=  ',
+      ),
+      pht('Whole word rewrite with whitespace prefix and suffix.'));
+
+    $this->assertSummaryProseParts(
+      "a\nb\nc\nd\ne\nf\ng\nh\n",
+      "a\nb\nc\nd\nX\nf\ng\nh\n",
+      array(
+        '.',
+        "= d\n",
+        '- e',
+        '+ X',
+        "= \nf",
+        '.',
+      ),
+      pht('Summary diff with middle change.'));
+
+    $this->assertSummaryProseParts(
+      "a\nb\nc\nd\ne\nf\ng\nh\n",
+      "X\nb\nc\nd\ne\nf\ng\nh\n",
+      array(
+        '- a',
+        '+ X',
+        "= \nb",
+        '.',
+      ),
+      pht('Summary diff with head change.'));
+
+    $this->assertSummaryProseParts(
+      "a\nb\nc\nd\ne\nf\ng\nh\n",
+      "a\nb\nc\nd\ne\nf\ng\nX\n",
+      array(
+        '.',
+        "= g\n",
+        '- h',
+        '+ X',
+        "= \n",
+      ),
+      pht('Summary diff with last change.'));
+
+    $this->assertProseParts(
+      'aaa aaa aaa aaa, bbb bbb bbb bbb.',
+      "aaa aaa aaa aaa, bbb bbb bbb bbb.\n\n- ccc ccc ccc",
+      array(
+        '= aaa aaa aaa aaa, bbb bbb bbb bbb.',
+        "+ \n\n- ccc ccc ccc",
+      ),
+      pht('Diff with new trailing content.'));
+
+    $this->assertProseParts(
+      'aaa aaa aaa aaa, bbb bbb bbb bbb.',
+      'aaa aaa aaa aaa bbb bbb bbb bbb.',
+      array(
+        '= aaa aaa aaa aaa',
+        '- ,',
+        '=  bbb bbb bbb bbb.',
+      ),
+      pht('Diff with a removed comma.'));
+
+    $this->assertProseParts(
+      'aaa aaa aaa aaa, bbb bbb bbb bbb.',
+      "aaa aaa aaa aaa bbb bbb bbb bbb.\n\n- ccc ccc ccc!",
+      array(
+        '= aaa aaa aaa aaa',
+        '- ,',
+        '=  bbb bbb bbb bbb.',
+        "+ \n\n- ccc ccc ccc!",
+      ),
+      pht('Diff with a removed comma and new trailing content.'));
+
+    $this->assertProseParts(
+      '[ ] Walnuts',
+      '[X] Walnuts',
+      array(
+        '= [',
+        '-  ',
+        '+ X',
+        '= ] Walnuts',
+      ),
+      pht('Diff adding a tickmark to a checkbox list.'));
+
+    $this->assertProseParts(
+      '[[ ./week49 ]]',
+      '[[ ./week50 ]]',
+      array(
+        '= [[ ./week',
+        '- 49',
+        '+ 50',
+        '=  ]]',
+      ),
+      pht('Diff changing a remarkup wiki link target.'));
+
+    // Create a large corpus with many sentences and paragraphs.
+    $large_paragraph = 'xyz. ';
+    $large_paragraph = str_repeat($large_paragraph, 50);
+    $large_paragraph = rtrim($large_paragraph);
+
+    $large_corpus = $large_paragraph."\n\n";
+    $large_corpus = str_repeat($large_corpus, 50);
+    $large_corpus = rtrim($large_corpus);
+
+    $this->assertProseParts(
+      $large_corpus,
+      "aaa\n\n".$large_corpus."\n\nzzz",
+      array(
+        "+ aaa\n\n",
+        '= '.$large_corpus,
+        "+ \n\nzzz",
+      ),
+      pht('Adding initial and final lines to a large corpus.'));
+
+  }
+
+  private function assertProseParts($old, $new, array $expect_parts, $label) {
+    $engine = new PhutilProseDifferenceEngine();
+    $diff = $engine->getDiff($old, $new);
+
+    $parts = $diff->getParts();
+
+    $this->assertParts($expect_parts, $parts, $label);
+  }
+
+  private function assertSummaryProseParts(
+    $old,
+    $new,
+    array $expect_parts,
+    $label) {
+
+    $engine = new PhutilProseDifferenceEngine();
+    $diff = $engine->getDiff($old, $new);
+
+    $parts = $diff->getSummaryParts();
+
+    $this->assertParts($expect_parts, $parts, $label);
+  }
+
+  private function assertParts(
+    array $expect,
+    array $actual_parts,
+    $label) {
+
+    $actual = array();
+    foreach ($actual_parts as $actual_part) {
+      $type = $actual_part['type'];
+      $text = $actual_part['text'];
+
+      switch ($type) {
+        case '.':
+          $actual[] = $type;
+          break;
+        default:
+          $actual[] = "{$type} {$text}";
+          break;
+      }
+    }
+
+    $this->assertEqual($expect, $actual, $label);
+  }
+
+
+}

src/infrastructure/diff/view/PHUIDiffOneUpInlineCommentRowScaffold.php

@@ -17,7 +17,7 @@ final class PHUIDiffOneUpInlineCommentRowScaffold
     $inline = head($inlines);
 
     $attrs = array(
-      'colspan' => 3,
+      'colspan' => 2,
       'id' => $inline->getScaffoldCellID(),
     );
 
@@ -32,6 +32,7 @@ final class PHUIDiffOneUpInlineCommentRowScaffold
     $cells = array(
       phutil_tag('td', array('class' => 'n'), $left_hidden),
       phutil_tag('td', array('class' => 'n'), $right_hidden),
+      phutil_tag('td', array('class' => 'copy')),
       phutil_tag('td', $attrs, $inline),
     );
 

src/infrastructure/graph/ManiphestTaskGraph.php

@@ -84,9 +84,18 @@ final class ManiphestTaskGraph
         ' ',
         $link,
       );
+
+      $subtype_tag = null;
+
+      $subtype = $object->newSubtypeObject();
+      if ($subtype && $subtype->hasTagView()) {
+        $subtype_tag = $subtype->newTagView()
+          ->setSlimShady(true);
+      }
     } else {
       $status = null;
       $assigned = null;
+      $subtype_tag = null;
       $link = $viewer->renderHandle($phid);
     }
 
@@ -115,18 +124,23 @@ final class ManiphestTaskGraph
       $marker,
       $trace,
       $status,
+      $subtype_tag,
       $assigned,
       $link,
     );
   }
 
   protected function newTable(AphrontTableView $table) {
+    $subtype_map = id(new ManiphestTask())->newEditEngineSubtypeMap();
+    $has_subtypes = ($subtype_map->getCount() > 1);
+
     return $table
       ->setHeaders(
         array(
           null,
           null,
           pht('Status'),
+          pht('Subtype'),
           pht('Assigned'),
           pht('Task'),
         ))
@@ -136,12 +150,15 @@ final class ManiphestTaskGraph
           'threads',
           'graph-status',
           null,
+          null,
           'wide pri object-link',
         ))
       ->setColumnVisibility(
         array(
           true,
           !$this->getRenderOnlyAdjacentNodes(),
+          true,
+          $has_subtypes,
         ))
       ->setDeviceVisibility(
         array(
@@ -150,6 +167,11 @@ final class ManiphestTaskGraph
           // On mobile, we only show the actual graph drawing if we're on the
           // standalone page, since it can take over the screen otherwise.
           $this->getIsStandalone(),
+          true,
+
+          // On mobile, don't show subtypes since they're relatively less
+          // important and we're more pressured for space.
+          false,
         ));
   }
 
@@ -180,6 +202,7 @@ final class ManiphestTaskGraph
       null,
       null,
       null,
+      null,
       pht("\xC2\xB7 \xC2\xB7 \xC2\xB7"),
     );
   }

src/infrastructure/markup/PhabricatorMarkupEngine.php

@@ -539,6 +539,7 @@ final class PhabricatorMarkupEngine extends Phobject {
     $rules[] = new PhutilRemarkupDelRule();
     $rules[] = new PhutilRemarkupUnderlineRule();
     $rules[] = new PhutilRemarkupHighlightRule();
+    $rules[] = new PhutilRemarkupAnchorRule();
 
     foreach (self::loadCustomInlineRules() as $rule) {
       $rules[] = clone $rule;

src/infrastructure/markup/__tests__/PhabricatorAnchorTestCase.php

@@ -0,0 +1,38 @@
+<?php
+
+final class PhabricatorAnchorTestCase
+  extends PhabricatorTestCase {
+
+  public function testAnchors() {
+
+    $low_ascii = '';
+    for ($ii = 19; $ii <= 127; $ii++) {
+      $low_ascii .= chr($ii);
+    }
+
+    $snowman = "\xE2\x9B\x84";
+
+    $map = array(
+      '' => '',
+      'Bells and Whistles' => 'bells-and-whistles',
+      'Termination for Nonpayment' => 'termination-for-nonpayment',
+      $low_ascii => '0123456789-abcdefghijklmnopqrstu',
+      'xxxx xxxx xxxx xxxx xxxx on' => 'xxxx-xxxx-xxxx-xxxx-xxxx',
+      'xxxx xxxx xxxx xxxx xxxx ox' => 'xxxx-xxxx-xxxx-xxxx-xxxx-ox',
+      "So, You Want To Build A {$snowman}?" =>
+        "so-you-want-to-build-a-{$snowman}",
+      str_repeat($snowman, 128) => str_repeat($snowman, 32),
+    );
+
+    foreach ($map as $input => $expect) {
+      $anchor = PhutilRemarkupHeaderBlockRule::getAnchorNameFromHeaderText(
+        $input);
+
+      $this->assertEqual(
+        $expect,
+        $anchor,
+        pht('Anchor for "%s".', $input));
+    }
+  }
+
+}

src/infrastructure/markup/blockrule/PhutilRemarkupHeaderBlockRule.php

@@ -73,24 +73,7 @@ final class PhutilRemarkupHeaderBlockRule extends PhutilRemarkupBlockRule {
   }
 
   private function generateAnchor($level, $text) {
-    $anchor = strtolower($text);
-    $anchor = preg_replace('/[^a-z0-9]/', '-', $anchor);
-    $anchor = preg_replace('/--+/', '-', $anchor);
-    $anchor = trim($anchor, '-');
-    $anchor = substr($anchor, 0, 24);
-    $anchor = trim($anchor, '-');
-    $base = $anchor;
-
-    $key = self::KEY_HEADER_TOC;
     $engine = $this->getEngine();
-    $anchors = $engine->getTextMetadata($key, array());
-
-    $suffix = 1;
-    while (!strlen($anchor) || isset($anchors[$anchor])) {
-      $anchor = $base.'-'.$suffix;
-      $anchor = trim($anchor, '-');
-      $suffix++;
-    }
 
     // When a document contains a link inside a header, like this:
     //
@@ -100,12 +83,30 @@ final class PhutilRemarkupHeaderBlockRule extends PhutilRemarkupBlockRule {
     // header itself. We push the 'toc' state so all the link rules generate
     // just names.
     $engine->pushState('toc');
-      $text = $this->applyRules($text);
+      $plain_text = $text;
-      $text = $engine->restoreText($text);
+      $plain_text = $this->applyRules($plain_text);
-
+      $plain_text = $engine->restoreText($plain_text);
-      $anchors[$anchor] = array($level, $text);
     $engine->popState('toc');
 
+    $anchor = self::getAnchorNameFromHeaderText($plain_text);
+
+    if (!strlen($anchor)) {
+      return null;
+    }
+
+    $base = $anchor;
+
+    $key = self::KEY_HEADER_TOC;
+    $anchors = $engine->getTextMetadata($key, array());
+
+    $suffix = 1;
+    while (isset($anchors[$anchor])) {
+      $anchor = $base.'-'.$suffix;
+      $anchor = trim($anchor, '-');
+      $suffix++;
+    }
+
+    $anchors[$anchor] = array($level, $plain_text);
     $engine->setTextMetadata($key, $anchors);
 
     return phutil_tag(
@@ -159,4 +160,26 @@ final class PhutilRemarkupHeaderBlockRule extends PhutilRemarkupBlockRule {
     return phutil_implode_html("\n", $toc);
   }
 
+  public static function getAnchorNameFromHeaderText($text) {
+    $anchor = phutil_utf8_strtolower($text);
+    $anchor = PhutilRemarkupAnchorRule::normalizeAnchor($anchor);
+
+    // Truncate the fragment to something reasonable.
+    $anchor = id(new PhutilUTF8StringTruncator())
+      ->setMaximumGlyphs(32)
+      ->setTerminator('')
+      ->truncateString($anchor);
+
+    // If the fragment is terminated by a word which "The U.S. Government
+    // Printing Office Style Manual" normally discourages capitalizing in
+    // titles, discard it. This is an arbitrary heuristic intended to avoid
+    // awkward hanging words in anchors.
+    $anchor = preg_replace(
+      '/-(a|an|the|at|by|for|in|of|on|per|to|up|and|as|but|if|or|nor)\z/',
+      '',
+      $anchor);
+
+    return $anchor;
+  }
+
 }

src/infrastructure/markup/markuprule/PhutilRemarkupAnchorRule.php

@@ -0,0 +1,69 @@
+<?php
+
+final class PhutilRemarkupAnchorRule extends PhutilRemarkupRule {
+
+  public function getPriority() {
+    return 200.0;
+  }
+
+  public function apply($text) {
+    return preg_replace_callback(
+      '/{anchor\s+#([^\s}]+)}/s',
+      array($this, 'markupAnchor'),
+      $text);
+  }
+
+  protected function markupAnchor(array $matches) {
+    $engine = $this->getEngine();
+
+    if ($engine->isTextMode()) {
+      return null;
+    }
+
+    if ($engine->isHTMLMailMode()) {
+      return null;
+    }
+
+    if ($engine->isAnchorMode()) {
+      return null;
+    }
+
+    if (!$this->isFlatText($matches[0])) {
+      return $matches[0];
+    }
+
+    if (!self::isValidAnchorName($matches[1])) {
+      return $matches[0];
+    }
+
+    $tag_view = phutil_tag(
+      'a',
+      array(
+        'name' => $matches[1],
+      ),
+      '');
+
+    return $this->getEngine()->storeText($tag_view);
+  }
+
+  public static function isValidAnchorName($anchor_name) {
+    $normal_anchor = self::normalizeAnchor($anchor_name);
+
+    if ($normal_anchor === $anchor_name) {
+      return true;
+    }
+
+    return false;
+  }
+
+  public static function normalizeAnchor($anchor) {
+    // Replace all latin characters which are not "a-z" or "0-9" with "-".
+    // Preserve other characters, since non-latin letters and emoji work
+    // fine in anchors.
+    $anchor = preg_replace('/[\x00-\x2F\x3A-\x60\x7B-\x7F]+/', '-', $anchor);
+    $anchor = trim($anchor, '-');
+
+    return $anchor;
+  }
+
+}

src/infrastructure/markup/markuprule/PhutilRemarkupBoldRule.php

@@ -18,6 +18,10 @@ final class PhutilRemarkupBoldRule extends PhutilRemarkupRule {
   }
 
   protected function applyCallback(array $matches) {
+    if ($this->getEngine()->isAnchorMode()) {
+      return $matches[1];
+    }
+
     return hsprintf('<strong>%s</strong>', $matches[1]);
   }
 

src/infrastructure/markup/remarkup/PhutilRemarkupEngine.php

@@ -34,6 +34,10 @@ final class PhutilRemarkupEngine extends PhutilMarkupEngine {
     return $this->mode & self::MODE_TEXT;
   }
 
+  public function isAnchorMode() {
+    return $this->getState('toc');
+  }
+
   public function isHTMLMailMode() {
     return $this->mode & self::MODE_HTML_MAIL;
   }

src/infrastructure/markup/remarkup/__tests__/remarkup/toc.txt

@@ -6,14 +6,14 @@
 
 ~~~~~~~~~~
 <ul>
-<li><a href="#http-www-example-com-lin">link_name</a></li>
+<li><a href="#link-name">link_name</a></li>
 <ul>
-<li><a href="#bold"><strong>bold</strong></a></li>
+<li><a href="#bold">bold</a></li>
 </ul>
 <li><a href="#http-www-example-com">http://www.example.com</a></li>
 </ul>
 
-<h2 class="remarkup-header"><a name="http-www-example-com-lin"></a><a href="http://www.example.com/" class="remarkup-link" target="_blank" rel="noreferrer">link_name</a></h2>
+<h2 class="remarkup-header"><a name="link-name"></a><a href="http://www.example.com/" class="remarkup-link" target="_blank" rel="noreferrer">link_name</a></h2>
 
 <h3 class="remarkup-header"><a name="bold"></a><strong>bold</strong></h3>
 

webroot/rsrc/css/application/differential/changeset-view.css

@@ -63,6 +63,11 @@
   padding: 1px 8px;
 }
 
+.differential-diff td.diff-flush {
+  padding-top: 0;
+  padding-bottom: 0;
+}
+
 .device .differential-diff td {
   padding: 1px 4px;
 }
@@ -282,18 +287,16 @@ td.cov-I {
   font-weight: bold;
 }
 
-.differential-diff .differential-image-diff {
+.differential-diff td.diff-image-cell {
+  background-color: transparent;
   background-image: url(/rsrc/image/checker_light.png);
-}
-
-.differential-diff .differential-image-diff:hover {
-  background-image: url(/rsrc/image/checker_dark.png);
-}
-
-.differential-diff .differential-image-diff td {
   padding: 8px;
 }
 
+.device-desktop .differential-diff .diff-image-cell:hover {
+  background-image: url(/rsrc/image/checker_dark.png);
+}
+
 .differential-image-stage {
   overflow: auto;
 }

webroot/rsrc/css/core/syntax.css

@@ -6,6 +6,10 @@
   color: #aa0066;
 }
 
+.remarkup-code .language-tag {
+  color: {$lightgreytext};
+}
+
 .remarkup-code td > span {
   display: inline;
   word-break: break-all;

webroot/rsrc/css/phui/phui-property-list-view.css

@@ -268,6 +268,10 @@ div.phui-property-list-stacked .phui-property-list-properties
   margin: 20px;
 }
 
+.document-engine-jupyter.document-engine-diff {
+  margin: 0;
+}
+
 .document-engine-in-flight {
   opacity: 0.25;
 }
@@ -294,22 +298,66 @@ div.phui-property-list-stacked .phui-property-list-properties
 
 .jupyter-cell-code {
   white-space: pre-wrap;
+  word-break: break-word;
   background: {$lightgreybackground};
-  padding: 8px;
-  border: 1px solid {$lightgreyborder};
   border-radius: 2px;
+  border-color: {$lightgreyborder};
+  border-style: solid;
+}
+
+.jupyter-cell-code-block {
+  padding: 8px;
+  border-width: 1px;
+}
+
+.jupyter-cell-code-line {
+  padding: 2px 8px;
+  border-width: 0 1px;
+}
+
+td.new .jupyter-cell-code-line {
+  background: {$new-background};
+  border-color: {$new-bright};
+}
+
+td.old .jupyter-cell-code-line {
+  background: {$old-background};
+  border-color: {$old-bright};
+}
+
+.jupyter-cell-code-head {
+  border-top-width: 1px;
+  margin-top: 4px;
+  padding-top: 8px;
+}
+
+.jupyter-cell-code-last {
+  border-bottom-width: 1px;
+  margin-bottom: 4px;
+  padding-bottom: 8px;
 }
 
-.jupyter-notebook > tbody > tr > th,
 .jupyter-notebook > tbody > tr > td {
   padding: 8px;
 }
 
-.jupyter-notebook > tbody > tr > th {
+.jupyter-notebook > tbody > tr > td.jupyter-cell-flush {
+  padding-top: 0;
+  padding-bottom: 0;
+}
+
+.jupyter-notebook,
+.jupyter-notebook > tbody > tr > td {
+  width: 100%;
+}
+
+.jupyter-notebook > tbody > tr > td.jupyter-label {
   white-space: nowrap;
   text-align: right;
-  min-width: 48px;
+  min-width: 56px;
   font-weight: bold;
+  width: auto;
+  padding: 8px 8px 0;
 }
 
 .jupyter-output {
@@ -326,3 +374,7 @@ div.phui-property-list-stacked .phui-property-list-properties
 .jupyter-output-html {
   background: {$sh-indigobackground};
 }
+
+.jupyter-cell-markdown {
+  white-space: pre-wrap;
+}

webroot/rsrc/js/application/diff/DiffChangeset.js

@@ -24,6 +24,7 @@ JX.install('DiffChangeset', {
     this._ref = data.ref;
     this._renderer = data.renderer;
     this._highlight = data.highlight;
+    this._documentEngine = data.documentEngine;
     this._encoding = data.encoding;
     this._loaded = data.loaded;
     this._treeNodeID = data.treeNodeID;
@@ -47,6 +48,7 @@ JX.install('DiffChangeset', {
     _ref: null,
     _renderer: null,
     _highlight: null,
+    _documentEngine: null,
     _encoding: null,
     _undoTemplates: null,
 
@@ -310,6 +312,7 @@ JX.install('DiffChangeset', {
         ref: this._ref,
         renderer: this.getRenderer() || '',
         highlight: this._highlight || '',
+        engine: this._documentEngine || '',
         encoding: this._encoding || ''
       };
     },
@@ -366,6 +369,14 @@ JX.install('DiffChangeset', {
       return this._highlight;
     },
 
+    setDocumentEngine: function(engine) {
+      this._documentEngine = engine;
+    },
+
+    getDocumentEngine: function(engine) {
+      return this._documentEngine;
+    },
+
     getSelectableItems: function() {
       var items = [];
 

webroot/rsrc/js/application/diff/DiffChangesetList.js

@@ -827,6 +827,26 @@ JX.install('DiffChangesetList', {
         });
       list.addItem(highlight_item);
 
+      var engine_item = new JX.PHUIXActionView()
+        .setIcon('fa-file-image-o')
+        .setName(pht('View As...'))
+        .setHandler(function(e) {
+          var params = {
+            engine: changeset.getDocumentEngine(),
+          };
+
+          new JX.Workflow('/services/viewas/', params)
+            .setHandler(function(r) {
+              changeset.setDocumentEngine(r.engine);
+              changeset.reload();
+            })
+            .start();
+
+          e.prevent();
+          menu.close();
+        });
+      list.addItem(engine_item);
+
       add_link('fa-arrow-left', pht('Show Raw File (Left)'), data.leftURI);
       add_link('fa-arrow-right', pht('Show Raw File (Right)'), data.rightURI);
       add_link('fa-pencil', pht('Open in Editor'), data.editor, true);
@@ -860,6 +880,7 @@ JX.install('DiffChangesetList', {
 
         encoding_item.setDisabled(!changeset.isLoaded());
         highlight_item.setDisabled(!changeset.isLoaded());
+        engine_item.setDisabled(!changeset.isLoaded());
 
         if (changeset.isLoaded()) {
           if (changeset.getRenderer() == '2up') {
@@ -1174,30 +1195,26 @@ JX.install('DiffChangesetList', {
         bot = tmp;
       }
 
-      // Find the leftmost cell that we're going to highlight: this is the next
+      // Find the leftmost cell that we're going to highlight. This is the
-      // <td /> in the row. In 2up views, it should be directly adjacent. In
+      // next sibling with a "data-copy-mode" attribute, which is a marker
-      // 1up views, we may have to skip over the other line number column.
+      // for the cell with actual content in it.
-      var l = top;
+      var content_cell = top;
-      while (JX.DOM.isType(l, 'th')) {
+      while (content_cell && !content_cell.getAttribute('data-copy-mode')) {
-        l = l.nextSibling;
+        content_cell = content_cell.nextSibling;
       }
 
-      // Find the rightmost cell that we're going to highlight: this is the
+      // If we didn't find a cell to highlight, don't highlight anything.
-      // farthest consecutive, adjacent <td /> in the row. Sometimes the left
+      if (!content_cell) {
-      // and right nodes are the same (left side of 2up view); sometimes we're
+        return;
-      // going to highlight several nodes (copy + code + coverage).
-      var r = l;
-      while (r.nextSibling && JX.DOM.isType(r.nextSibling, 'td')) {
-        r = r.nextSibling;
       }
 
-      var pos = JX.$V(l)
+      var pos = JX.$V(content_cell)
-        .add(JX.Vector.getAggregateScrollForNode(l));
+        .add(JX.Vector.getAggregateScrollForNode(content_cell));
 
-      var dim = JX.$V(r)
+      var dim = JX.$V(content_cell)
-        .add(JX.Vector.getAggregateScrollForNode(r))
+        .add(JX.Vector.getAggregateScrollForNode(content_cell))
         .add(-pos.x, -pos.y)
-        .add(JX.Vector.getDim(r));
+        .add(JX.Vector.getDim(content_cell));
 
       var bpos = JX.$V(bot)
         .add(JX.Vector.getAggregateScrollForNode(bot));

webroot/rsrc/js/core/behavior-watch-anchor.js

@@ -8,52 +8,102 @@
 
 JX.behavior('phabricator-watch-anchor', function() {
 
-  var highlighted;
+  // When the user loads a page with an "#anchor" or changes the "#anchor" on
+  // an existing page, we try to scroll the page to the relevant location.
 
-  function highlight() {
+  // Browsers do this on their own, but we have some additional rules to try
-    highlighted && JX.DOM.alterClass(highlighted, 'anchor-target', false);
+  // to match anchors more flexibly and handle cases where an anchor is not
-    try {
+  // yet present in the document because something is still loading or
-      highlighted = JX.$('anchor-' + window.location.hash.replace('#', ''));
+  // rendering it, often via Ajax.
-    } catch (ex) {
-      highlighted = null;
-    }
-    highlighted && JX.DOM.alterClass(highlighted, 'anchor-target', true);
-  }
 
-  // Defer invocation so other listeners can update the document.
+  // Number of milliseconds we'll keep trying to find an anchor for.
-  function defer_highlight() {
+  var wait_max = 5000;
-    setTimeout(highlight, 0);
+
-  }
+  // Wait between retries.
+  var wait_ms = 100;
+
+  var target;
+  var retry_ms;
 
-  // In some cases, we link to an anchor but the anchor target ajaxes in
-  // later. If it pops in within the first few seconds, jump to it.
   function try_anchor() {
-    var anchor = window.location.hash.replace('#', '');
+    retry_ms = wait_max;
-    try {
+    seek_anchor();
-      // If the anchor exists, assume the browser handled the jump.
-      if (anchor) {
-        JX.$(anchor);
   }
-      defer_highlight();
+
-    } catch (e) {
+  function seek_anchor() {
-      var n = 50;
+    var anchor = window.location.hash.replace('#', '');
-      var try_anchor_again = function () {
+
+    if (!anchor.length) {
+      return;
+    }
+
+    var ii;
+    var node = null;
+
+    // When the user navigates to "#abc", we'll try to find a node with
+    // either ID "abc" or ID "anchor-abc".
+    var ids = [anchor, 'anchor-' + anchor];
+
+    for (ii = 0; ii < ids.length; ii++) {
+      try {
+        node = JX.$(ids[ii]);
+        break;
+      } catch (e) {
+        // Continue.
+      }
+    }
+
+    // If we haven't found a matching node yet, look for an "<a />" tag with
+    // a "name" attribute that has our anchor as a prefix. For example, you
+    // can navigate to "#cat" and we'll match "#cat-and-mouse".
+
+    if (!node) {
+      var anchor_nodes = JX.DOM.scry(document.body, 'a');
+      for (ii = 0; ii < anchor_nodes.length; ii++) {
+        if (!anchor_nodes[ii].name) {
+          continue;
+        }
+
+        if (anchor_nodes[ii].name.substring(0, anchor.length) === anchor) {
+          node = anchor_nodes[ii];
+          break;
+        }
+      }
+    }
+
+    // If we already have an anchor highlighted, unhighlight it and throw
+    // it away if it doesn't match the new target.
+    if (target && (target !== node)) {
+      JX.DOM.alterClass(target, 'anchor-target', false);
+      target = null;
+    }
+
+    // If we didn't find a matching anchor, try again soon. This allows
+    // rendering logic some time to complete Ajax requests and draw elements
+    // onto the page.
+    if (!node) {
+      if (retry_ms > 0) {
+        retry_ms -= wait_ms;
+        setTimeout(try_anchor, wait_ms);
+        return;
+      }
+    }
+
+    // If we've found a new target, highlight it.
+    if (target !== node) {
+      target = node;
+      JX.DOM.alterClass(target, 'anchor-target', true);
+    }
+
+    // Try to scroll to the new target.
     try {
-          var node = JX.$(anchor);
       var pos = JX.Vector.getPosWithScroll(node);
       JX.DOM.scrollToPosition(0, pos.y - 60);
-          defer_highlight();
     } catch (e) {
-          if (n--) {
+      // Ignore issues with scrolling the document.
-            setTimeout(try_anchor_again, 100);
-          }
-        }
-      };
-      try_anchor_again();
     }
   }
 
   JX.Stratcom.listen('hashchange', null, try_anchor);
   try_anchor();
-
 });