Umbrella ticket for maintenance and code quality tasks within the current #WMDE-QWERTY-Sprint-2019-05-15 that are not strictly necessary for a user-facing story.
* A larger series of patches restructuring code in the FileImporter extension. Mostly part of T212199 as well as T213821 and T198584, but not necessarily all tagged with these ticket numbers.
* Tagged and released Wikidiff2 to allow soon deployment of the bugfix and performance improvements: ( also part of T223391#5190777 )
* Fix the fade-out gradient in #reference_previews sometimes not disappearing: https://gerrit.wikimedia.org/r/511384
* Removed Ruby browser tests from #two-column-edit-conflict-merge to avoid failing tests: ( also part of T222714 )
* Fix #two-column-edit-conflict-merge browser tests failing due to VisualEditor
* CI enhancements and stability, T223967
* Fix an incomplete hook documentation, relevant for FileImporter: https://gerrit.wikimedia.org/r/510990
* Fix a circular dependency in #cognate: https://gerrit.wikimedia.org/r/507752
* …