MediaWiki 1.21/wmf6

Deployment of MediaWiki 1.21wmf6 to Wikimedia sites
The latest version (labeled "1.21wmf6 ") of MediaWiki, the software that powers Wikipedia and its sister sites, was deployed to all Wikimedia sites in stages (see the roadmap).

We will continue to deploy the latest software every two weeks. This is intended to minimize disruption and possible issues, and make it easier to identify the cause of problems, since the possibly problematic code will be much more recent.

Core changes

 * - Revert UIDGenerator commits.
 * - test: detects parent setUp not being called
 * - Update docs for DifferenceEngine::getDiff
 * - Update misleading variable names in docs
 * - better handling of minor/bot in enhanced changelist
 * - add cursor:pointer to .mw-enhancedchanges-arrow
 * - Adjust comment for log_params database field
 * - [JobQueue] Removed redundant DBO_TRX handling in JobQueueDB.
 * - Add type hint
 * - Cleaned up UIDGenerator docs a bit.
 * - fix sort order
 * - Add UIDGenerator to AutoLoader
 * - Class for getting statistically unique IDs NOT a RFC4122 standard string representation
 * - New parser tests to spec wikitext behavior found on en:WP
 * - Added a few tests to spec HTML-pre behavior and test Parsoid.
 * - add method to check if ORMTable exists
 * - Treat message cache loading as fatal
 * - Add wfDeprecated to wfMsg* methods from 1.21 on
 * - Add 1.20 RELEASE-NOTES to HISTORY
 * - Make Language::isValidBuiltInCode return bool
 * - Avoid serializing database object in update.php
 * - [Upload] [Schema] Added us_props column to avoid expensive GETs.
 * - [JobQueue] Use SELECT for deduplication rather than more expensive DELETEs.
 * - (no bug) Fix per-connection db name in ORMTable.
 * - Make deleteOldRevisions.php no longer throw database errors on empty sets.
 * - Add timestamp sort to list=allimages
 * - test: raise timeout for DatabaseSqlite
 * - test: raise timeout for ExifRotation
 * - Fix API action=options&amp;reset=1 &amp; unit tests
 * - Set robot meta tags for 'view source' pages
 * - mediawiki.Uri: Don't raw encode the 'title' query parameter.
 * - Database: fname was not logged for BEGIN/COMMIT.
 * - Show comment not as block in tables
 * - Fixing typo
 * - Add some __METHOD__ to begin/commit/rollback calls
 * - mediawiki.Uri: Update doc comments.
 * - Changed the wording of the protectedpagetext message to include moving and other actions.
 * - Implement static public Parser::getExternalLinkRel
 * - Refactor edit notice rendering so that it's not baked into EditPage
 * - Test / spec handling of HTML entities in link tails
 * - Fixed documentation
 * - Added assertException method to MediaWikiTestCase
 * - Validate preference values in action=options
 * - MediaWiki:Contributions should support gender
 * - Validate editfont before embedding it in CSS
 * - Remove the throw from Message::extractParam
 * - Add comments to Linker::formatLinksInComment
 * - Optimized regex in Linker.php
 * - Refresh SessionId on login
 * - Add a hook to Special:Version so we can customize the version URL
 * - Test handling of templates with invalid template target
 * - Change msg check sp-contributions-explain from exists to isBlank
 * - Genderize be-tarask namespaces, fix spaces in definitions
 * - Additional table tests to spec parser behavior.
 * - Improve type hint
 * - Test table / list interaction
 * - API: Fix description for YAML format
 * - MWTimestamp::getHumanTimestamp uses 'just-now' message, which did not exist
 * - Addition of SearchAfterNoDirectMatch hook
 * - [JobQueue] Improved refreshLinks/htmlCacheUpdate job de-duplication.
 * - Store &quot;bad metadata&quot; placeholder metadata for SVGs.
 * - Added a script to populate file HTTP headers for existing files.
 * - Fix typo (sentances =&gt; sentences)
 * - Changed Status class to allow passing of Message objects.
 * - RefreshLinksJob parsed with incorrect revision variables
 * - Rebuild MessagesEn.php
 * - Fix $wgHtml5 case. Follow-up c35304 (0473c33)
 * - Made BackLinkCache use object caching better.
 * - Expand release notes
 * - release notes for I9a2ebd50
 * - Typo in comment's Example code.
 * - [JobQueue] Fixed some old race conditions in nextJobDB.php
 * -  Improve display of IPv6 addresses
 * - Move around User::getEditCount code.
 * - Make clear that reportConnectionError stops the code flow.
 * - $wgHTML5 is a different variable than $wgHtml5 and the right name is the later.
 * - Global tweaks wrt $wgSecureLogin.
 * - Removal of unused globals.
 * - Email notification mistakes log action for new page creation
 * - Fix doc/hooks.txt for EditPage::showStandardInputs:options
 * - Stopped some debug notice warnings from showing on SpecialPages.
 * - Fix data type for timestamp in TestORMRowTest
 * - provide a way to separate out schema changes
 * - Fix hash validation in api
 * - Add 'dimensions' and 'thumbmine' to resultproperties in prop=imageinfo
 * - Kill DeviceDetection
 * - Improve documentation for &quot;pipe trick&quot;