When processing an incoming email, we try to find a parent for the email based on references. Before this merge, it was done using openerp-<model-<res_id> pattern. However it is buggy. Indeed having two OpenERP sending emails to each other leads to messages being inserted in a wrong thread (model and res_id of the first OpenERP for both instances).
Now we search for an exact match between the references and the stored message_ids. As each message_id can be considered as unique the number of collisions is lessened. This won't cause any issues with OpenERP >= 7.0.
A compatibility mode is implemented for <= 6.1: as in those versions the message_id is not stored, we fall back on the previous behavior for records having messages without message_id. This indicates that the record was created before 7.0.
Tests have been updated accordingly, and a test added for the compatibility mode.
bzr revid: tde@openerp.com-20131205100534-2rlyun8wqng3qa6f
896fab1b44