Revision contexts and negotiation

[pmelab]

A revision can store multiple context associations (e.g. the associated workspace) within the revision table. These context values can be used to identify the "current" revision for a given context or to compare revision between context branches.

This currently is based on a RevisionTreeQuery service that provides pre-built SQL queries that can be used in joins or sub-selects. The queries built are non-optimized and an obvious performance problem, but they work in the way we intend them too. They could be optimized by operating on an index that is written on revision creation instead on the revision tables directly.

• Context field information for workspaces
• Interface for the contextual revision query builder
• SQL implementation of the contextual revision query builder
• Param converter using getActive
• Entity query override providing activeRevisions
• Interface definition for getActive and getActiveMultiple
• Entity repository override with getActive and getActiveMultiple
• Test case for context query
• Test case for revision negotiation in entity repository

TODO:

• Revision tree index for performance

Resolution: TBD

[amateescu]

This needs to be discussed with @plach79 as well. The current plan is to try and make it a core patch, but we should fall back to contrib if it doesn't make it in time for 8.7.