Pick context windows for inlines in a slightly smarter way

Summary:
Ref T10694. This mostly prevents us from having a degenerate case if someone leaves a 200-line inline.

  - For one-line inlines, show 1 line of context above and below (3 lines total).
  - For 3+ line inlines, show just the inline.
  - For 7+ line inlines, show only the first part.

Test Plan: Made a bunch of weird long/short/different-sized comments, saw reasonble-appearing context in text and HTML mail output.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10694

Differential Revision: https://secure.phabricator.com/D15853

src/applications/differential/mail/DifferentialInlineCommentMailView.php

@@ -290,9 +290,27 @@ final class DifferentialInlineCommentMailView
     $start = $comment->getLineNumber();
     $length = $comment->getLineLength();
 
+    // By default, show one line of context around the target inline.
+    $context = 1;
+
+    // If the inline is at least 3 lines long, don't show any extra context.
+    if ($length >= 2) {
+      $context = 0;
+    }
+
+    // If the inline is more than 7 lines long, only show the first 7 lines.
+    if ($length >= 6) {
+      $length = 6;
+    }
+
     if (!$is_html) {
       $hunks = $changeset->getHunks();
-      $patch = $parser->makeContextDiff($hunks, $is_new, $start, $length, 1);
+      $patch = $parser->makeContextDiff(
+        $hunks,
+        $is_new,
+        $start,
+        $length,
+        $context);
       $patch = phutil_split_lines($patch);
 
       // Remove the "@@ -x,y +u,v @@" line.
@@ -318,7 +336,10 @@ final class DifferentialInlineCommentMailView
 
     $parser->setRenderer(new DifferentialChangesetOneUpMailRenderer());
 
-    return $parser->render($start - 1, $length + 3, array());
+    return $parser->render(
+      $start - $context,
+      $length + 1 + (2 * $context),
+      array());
   }
 
   private function renderPatch(

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -852,7 +852,7 @@ final class DifferentialChangesetParser extends Phobject {
 
       $range_end = $this->getOffset($offset_map, $range_start + $range_len);
       $range_start = $this->getOffset($offset_map, $range_start);
-      $range_len = $range_end - $range_start;
+      $range_len = ($range_end - $range_start);
     }
 
     $render_pch = $this->shouldRenderPropertyChangeHeader($this->changeset);

src/applications/differential/render/DifferentialChangesetOneUpMailRenderer.php

@@ -73,6 +73,8 @@ final class DifferentialChangesetOneUpMailRenderer
             }
           }
 
+          $style = "padding: 0 2px; {$style}";
+
           $out[] = phutil_tag(
             'div',
             array(