Render prose diffs in email as summaries

Summary:
Ref T7643. When a large block of prose text is edited (like a wiki page), summarize the diff when sending mail.

For now, I'm still showing the whole thing in the web UI, since it's a bit more manageable there.

Also try to fix newlines in Airmail.

Test Plan:
This web diff:

{F1682591}

..became this mail diff:

{F1682592}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7643

Differential Revision: https://secure.phabricator.com/D16098

resources/celerity/map.php

@@ -10,7 +10,7 @@ return array(
     'core.pkg.css' => '6913fe66',
     'core.pkg.js' => '10275c16',
     'darkconsole.pkg.js' => 'e7393ebb',
-    'differential.pkg.css' => 'f3fb8324',
+    'differential.pkg.css' => 'b3eea3f5',
     'differential.pkg.js' => '4b7d8f19',
     'diffusion.pkg.css' => '91c5d3a6',
     'diffusion.pkg.js' => '3a9a8bfa',
@@ -57,7 +57,7 @@ return array(
     'rsrc/css/application/dashboard/dashboard.css' => 'bc6f2127',
     'rsrc/css/application/diff/inline-comment-summary.css' => '51efda3a',
     'rsrc/css/application/differential/add-comment.css' => 'c47f8c40',
-    'rsrc/css/application/differential/changeset-view.css' => '805f1141',
+    'rsrc/css/application/differential/changeset-view.css' => 'ccfbc869',
     'rsrc/css/application/differential/core.css' => '5b7b8ff4',
     'rsrc/css/application/differential/phui-inline-comment.css' => '5953c28e',
     'rsrc/css/application/differential/revision-comment.css' => '14b8565a',
@@ -553,7 +553,7 @@ return array(
     'conpherence-update-css' => 'faf6be09',
     'conpherence-widget-pane-css' => '775eaaba',
     'd3' => 'a11a5ff2',
-    'differential-changeset-view-css' => '805f1141',
+    'differential-changeset-view-css' => 'ccfbc869',
     'differential-core-view-css' => '5b7b8ff4',
     'differential-inline-comment-editor' => '64a5550f',
     'differential-revision-add-comment-css' => 'c47f8c40',
@@ -1528,9 +1528,6 @@ return array(
       'javelin-vector',
       'javelin-stratcom',
     ),
-    '805f1141' => array(
-      'phui-inline-comment-view-css',
-    ),
     '834a1173' => array(
       'javelin-behavior',
       'javelin-scrollbar',
@@ -1926,6 +1923,9 @@ return array(
       'javelin-util',
       'phabricator-notification-css',
     ),
+    'ccfbc869' => array(
+      'phui-inline-comment-view-css',
+    ),
     'cf86d16a' => array(
       'javelin-behavior',
       'javelin-dom',

src/applications/transactions/view/PhabricatorApplicationTransactionTextDiffDetailView.php

@@ -33,11 +33,24 @@ final class PhabricatorApplicationTransactionTextDiffDetailView
     );
     $new_styles = implode(' ', $new_styles);
 
+    $omit_styles = array(
+      'padding: 8px 0;',
+    );
+    $omit_styles = implode(' ', $omit_styles);
+
     $result = array();
-    foreach ($diff->getParts() as $part) {
+    foreach ($diff->getSummaryParts() as $part) {
       $type = $part['type'];
       $text = $part['text'];
       switch ($type) {
+        case '.':
+          $result[] = phutil_tag(
+            'div',
+            array(
+              'style' => $omit_styles,
+            ),
+            pht('...'));
+          break;
         case '-':
           $result[] = phutil_tag(
             'span',
@@ -62,8 +75,13 @@ final class PhabricatorApplicationTransactionTextDiffDetailView
 
     $styles = array(
       'white-space: pre-wrap;',
+      'color: #74777D;',
     );
 
+    // Beyond applying "pre-wrap", convert newlines to "<br />" explicitly
+    // to improve behavior in clients like Airmail.
+    $result = phutil_escape_html_newlines($result);
+
     return phutil_tag(
       'div',
       array(

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

@@ -95,6 +95,7 @@
 
 .prose-diff {
   white-space: pre-wrap;
+  color: {$greytext};
 }
 
 .prose-diff-frame {