(added in 1.13)
$status: Status object, modify this to throw an error. Overridden by $error
(added in 1.20)
+$suppress: Whether this is a suppression deletion or not (added in 1.27)
'ArticleDeleteAfterSuccess': Output after an article has been deleted.
$title: Title of the article that has been deleted.
$user: the user (object) marking the revision as patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user needs to be a
sysop in order to mark an edit patrolled.
+$auto true if the edit is being marked as patrolled automatically
'MarkPatrolledComplete': After an edit is marked patrolled.
$rcid: ID of the revision marked as patrolled
$user: user (object) who marked the edit patrolled
$wcOnlySysopsCanPatrol: config setting indicating whether the user must be a
sysop to patrol the edit.
+$auto true if the edit is being marked as patrolled automatically
'MediaWikiPerformAction': Override MediaWiki::performAction(). Use this to do
something completely different, after the basic globals have been set up, but
$to: Array of MailAddress objects for the recipients
&$returnPath: The return address string
+'UserMailerSplitTo': Called in UserMailer::send() to give extensions a chance
+to split up an email with multiple the To: field into separate emails.
+$to: array of MailAddress objects; unset the ones which should be mailed separately
+
+'UserMailerTransformContent': Called in UserMailer::send() to change email contents.
+Extensions can block sending the email by returning false and setting $error.
+$to: array of MailAdresses of the targets
+$from: MailAddress of the sender
+&$body: email body, either a string (for plaintext emails) or an array with 'text' and 'html' keys
+&$error: should be set to an error message string
+
+'UserMailerTransformMessage': Called in UserMailer::send() to change email after it has gone through
+the MIME transform. Extensions can block sending the email by returning false and setting $error.
+$to: array of MailAdresses of the targets
+$from: MailAddress of the sender
+&$subject: email subject (not MIME encoded)
+&$headers: email headers (except To: and Subject:) as an array of header name => value pairs
+&$body: email body (in MIME format) as a string
+&$error: should be set to an error message string
+
'UserRemoveGroup': Called when removing a group; return false to override stock
group removal.
$user: the user object that is to have a group removed