After experimenting with a BuildKit based solution in T268368: Summarize experiments with buildkit based MediaWiki image builds, it's apparent there are some risks to introducing a such a new technology. Let's try something similar but using PipelineLib/Blubber mostly as they are now (allowing for some refactoring of course) and compare results.

Abstract

Implement a process for building single-version MediaWiki images that:

1. Responds to merge events for wmf branches of core and extensions/skins
2. Uses PipelineLib and Blubber configuration from mediawiki-config to define workflow and image build.
3. Integrates all MW components (extensions, skins, vendor) from a local context of source files (single-version mediawiki directory hierarchy).
4. Is relatively fast (for a CI job, < 5 min).

Implementation of the above process will use existing Blubber and PipelineLib implementations with minor changes if necessary but no substantial reimplementation or new components.