Fix "request" and "update" mail preferences for Differential

Summary:
Fixes T3030. T1977 attempted to fix this but either didn't work (I think this is the case) or was broken later. We don't send `DifferentialCommentMail` on a create or update; we send `DifferentialReviewRequestMail`.

Also update the details to be more clear.

Test Plan:
Verified review request mail is marked undeliverable:

```
$ ./bin/mail show-outbound --id 6644
...
PARAMETERS
...
mailtags: ["differential-review-request"]
...
subject: D922: asdf
subject-prefix: [Differential]
vary-subject-prefix: [Request, 100 lines]
...
RECIPIENTS
! duck (duck)
    - This mail has tags which control which users receive it, and this recipient has not elected to receive mail with any of the tags on this message (Settings > Email Preferences).

BODY
epriestley requested code review of "asdf".
...
```

Verified update mail is marked undeliverable:

```
$ ./bin/mail show-outbound --id 6646
...
Message: Message has no valid recipients: all To/Cc are disabled, invalid, or configured not to receive this mail.

PARAMETERS
...
mailtags: ["differential-updated"]
...
subject: D922: asdf
subject-prefix: [Differential]
vary-subject-prefix: [Updated, 100 lines]
...
RECIPIENTS
! duck (duck)
    - This mail has tags which control which users receive it, and this recipient has not elected to receive mail with any of the tags on this message (Settings > Email Preferences).

BODY
epriestley updated the revision "asdf".
...
```

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T3030

Differential Revision: https://secure.phabricator.com/D6518

src/applications/differential/mail/DifferentialCommentMail.php

@@ -48,12 +48,6 @@ final class DifferentialCommentMail extends DifferentialMail {
       case DifferentialAction::ACTION_ADDREVIEWERS:
         $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEWERS;
         break;
-      case DifferentialAction::ACTION_UPDATE:
-        $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED;
-        break;
-      case DifferentialAction::ACTION_REQUEST:
-        $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEW_REQUEST;
-        break;
       case DifferentialAction::ACTION_COMMENT:
         // this is a comment which we will check separately below for content
         break;

src/applications/differential/mail/DifferentialReviewRequestMail.php

@@ -140,4 +140,14 @@ abstract class DifferentialReviewRequestMail extends DifferentialMail {
     }
   }
 
+  protected function getMailTags() {
+    $tags = array();
+    if ($this->isFirstMailToRecipients()) {
+      $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEW_REQUEST;
+    } else {
+      $tags[] = MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED;
+    }
+    return $tags;
+  }
+
 }

src/applications/settings/panel/PhabricatorSettingsPanelEmailPreferences.php

@@ -167,21 +167,34 @@ final class PhabricatorSettingsPanelEmailPreferences
             pht('This option adds more information to email subjects, but may '.
             'break threading in some clients.')));
 
-    $form
-      ->appendChild(hsprintf(
-        '<br />'.
-        '<p class="aphront-form-instructions">%s</p>'.
-        '<p class="aphront-form-instructions">'.
-          '<strong>%s</strong> %s</p>',
-        pht('You can customize what mail you receive from Phabricator here.'),
-        pht('NOTE:'),
-        pht('If an update makes several changes (like '.
-          'adding CCs to a task, closing it, and adding a comment) you will '.
-          'still receive an email as long as at least one of the changes '.
-          'is set to notify you.')));
-
     $mailtags = $preferences->getPreference('mailtags', array());
 
+    $form->appendChild(
+      id(new PHUIFormDividerControl()));
+
+    $form->appendRemarkupInstructions(
+      pht(
+        'You can customize which kinds of events you receive email for '.
+        'here. If you turn off email for a certain type of event, you '.
+        'will receive an unread notification in Phabricator instead.'.
+        "\n\n".
+        'Phabricator notifications (shown in the menu bar) which you receive '.
+        'an email for are marked read by default in Phabricator. If you turn '.
+        'off email for a certain type of event, the corresponding '.
+        'notification will not be marked read.'.
+        "\n\n".
+        'Note that if an update makes several changes (like adding CCs to a '.
+        'task, closing it, and adding a comment) you will still receive '.
+        'an email as long as at least one of the changes is set to notify '.
+        'you.'.
+        "\n\n".
+        'These preferences **only** apply to objects you are connected to '.
+        '(for example, Revisions where you are a reviewer or tasks you are '.
+        'CC\'d on). To receive email alerts when other objects are created, '.
+        'configure [[ /herald/ | Herald Rules ]].'.
+        "\n\n".
+        '**Phabricator will send an email to your primary account when:**'));
+
     $form
       ->appendChild(
         $this->buildMailTagCheckboxes(
@@ -217,35 +230,34 @@ final class PhabricatorSettingsPanelEmailPreferences
 
   private function getMailTags() {
     return array(
-      MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEWERS =>
-        pht("Send me email when a revision's reviewers change."),
-      MetaMTANotificationType::TYPE_DIFFERENTIAL_CLOSED =>
-        pht("Send me email when a revision is closed."),
-      MetaMTANotificationType::TYPE_DIFFERENTIAL_CC =>
-        pht("Send me email when a revision's CCs change."),
-      MetaMTANotificationType::TYPE_DIFFERENTIAL_COMMENT =>
-        pht("Send me email when a revision is commented on."),
-      MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED =>
-        pht("Send me email when a revision is updated."),
       MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEW_REQUEST =>
-        pht("Send me email when I am requested to review a revision."),
+        pht("A revision is created."),
+      MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED =>
+        pht("A revision is updated."),
+      MetaMTANotificationType::TYPE_DIFFERENTIAL_COMMENT =>
+        pht("Someone comments on a revision."),
+      MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEWERS =>
+        pht("A revision's reviewers change."),
+      MetaMTANotificationType::TYPE_DIFFERENTIAL_CLOSED =>
+        pht("A revision is closed."),
+      MetaMTANotificationType::TYPE_DIFFERENTIAL_CC =>
+        pht("A revision's CCs change."),
       MetaMTANotificationType::TYPE_DIFFERENTIAL_OTHER =>
-        pht("Send me email for any other activity not listed above."),
+        pht("Other revision activity not listed above occurs."),
-
       MetaMTANotificationType::TYPE_MANIPHEST_STATUS =>
-        pht("Send me email when a task's status changes."),
+        pht("A task's status changes."),
       MetaMTANotificationType::TYPE_MANIPHEST_OWNER =>
-        pht("Send me email when a task's owner changes."),
+        pht("A task's owner changes."),
-      MetaMTANotificationType::TYPE_MANIPHEST_PRIORITY =>
-        pht("Send me email when a task's priority changes."),
-      MetaMTANotificationType::TYPE_MANIPHEST_CC =>
-        pht("Send me email when a task's CCs change."),
-      MetaMTANotificationType::TYPE_MANIPHEST_PROJECTS =>
-        pht("Send me email when a task's associated projects change."),
       MetaMTANotificationType::TYPE_MANIPHEST_COMMENT =>
-        pht("Send me email when a task is commented on."),
+        pht("Someone comments on a task."),
+      MetaMTANotificationType::TYPE_MANIPHEST_PRIORITY =>
+        pht("A task's priority changes."),
+      MetaMTANotificationType::TYPE_MANIPHEST_CC =>
+        pht("A task's CCs change."),
+      MetaMTANotificationType::TYPE_MANIPHEST_PROJECTS =>
+        pht("A task's associated projects change."),
       MetaMTANotificationType::TYPE_MANIPHEST_OTHER =>
-        pht("Send me email for any other activity not listed above."),
+        pht("Other task activity not listed above occurs."),
 
     );
   }
@@ -268,12 +280,12 @@ final class PhabricatorSettingsPanelEmailPreferences
     return array_select_keys(
       $this->getMailTags(),
       array(
-        MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEWERS,
-        MetaMTANotificationType::TYPE_DIFFERENTIAL_CLOSED,
-        MetaMTANotificationType::TYPE_DIFFERENTIAL_CC,
-        MetaMTANotificationType::TYPE_DIFFERENTIAL_COMMENT,
-        MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED,
         MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEW_REQUEST,
+        MetaMTANotificationType::TYPE_DIFFERENTIAL_UPDATED,
+        MetaMTANotificationType::TYPE_DIFFERENTIAL_COMMENT,
+        MetaMTANotificationType::TYPE_DIFFERENTIAL_CLOSED,
+        MetaMTANotificationType::TYPE_DIFFERENTIAL_REVIEWERS,
+        MetaMTANotificationType::TYPE_DIFFERENTIAL_CC,
         MetaMTANotificationType::TYPE_DIFFERENTIAL_OTHER,
       ));
   }