=== Configuration changes in 1.27 ===
* Removed $wgUseLinkNamespaceDBFields
+* Deprecated $wgResourceLoaderMinifierStatementsOnOwnLine and
+ $wgResourceLoaderMinifierMaxLineLength, because there was little value in
+ making the behavior configurable. The default values (`false` for the former,
+ 1000 for the latter) are now hard-coded.
+* $wgDebugDumpSqlLength was removed (deprecated in 1.24).
+* $wgDebugDBTransactions was removed (deprecated in 1.20).
=== New features in 1.27 ===
+* $wgDataCenterId and $wgDataCenterRoles where added, which will serve as
+ basic configuration settings needed for multi-datacenter setups.
+ $wgDataCenterUpdateStickTTL was also added.
+* Added a new hook, 'UserMailerTransformContent', to transform the contents
+ of an email. This is similar to the EmailUser hook but applies to all mail
+ sent via UserMailer.
+* Added a new hook, 'UserMailerTransformMessage', to transform the contents
+ of an emai after MIME encoding.
+* Added a new hook, 'UserMailerSplitTo', to control which users have to be
+ emailed separately (ie. there is a single address in the To: field) so
+ user-specific changes to the email can be applied safely.
==== External libraries ====