merge with entity_name

[Mike Bayer]

need to define the semantics of how merge() works given transient entities with possible entity_names.

[Mike Bayer]

this ticket is a continuation of #540.

[Mike Bayer]

test case 1 - merging creates dupes

[Mike Bayer]

OK, changeset:2512 considers entity_name passed to merge() as overriding. also adds entity_name to relation() to make creating mappers easier, and has an attempt at merging fully while avoiding loops, but this logic needs more testing. the first test script also was merging to sqlite0 unnecessarily, so improved test will be attached.

we also need to put a check for "merging an object thats already in the session", which isnt here and would better detect those errors.

[Mike Bayer]

test case 2. improves test case 1 slightly and gets through to the end.

[Former user]

Further test case: saving an existing object only updates one database

[Mike Bayer]

for 0.4.xx, determine if current merge() functionality makes sense, ensure unit test coverage, then close. the user here was trying to do sharding via entity_name so that use case shouldnt be considered for this ticket.

[Mike Bayer]

entity_name is removed in 0.5

[Mike Bayer]

Removing milestone: 0.4.xx (automated comment)