All references to galaxy.model.tool_shed_install models should go through this instance. Right now it is a reference to the same ModelMapping instance, but the goal is to allow them to be two different mappings.
Shared across Tool Shed and Galaxy to reduce code duplication. Previously this was just a bunch, making it a real class allows placing some shared logic in there.
This refactoring also eliminates some global variables galaxy.model.mapping.Session, galaxy.model.mapping.context, and same for tool shed. This may break things, but these are things that should probably be fixed anyway.
In particular small changes to db_shell.py and a unit test that depended on these global variables have been updated. The functional test frameworks likewise needed to be updated to not depend on these - these changes were more substantial.
To fix these functional tests, I essentially replace old references to global variables in Galaxy with references to global variables just defined in the test framework in test/functional/database_contexts.py (a slight improvement).
John Chilton