[IMP] models: change API of `_group_by_full`

The dictionary `_group_by_full` is replaced by a field parameter `group_expand`
that is assigned to the method name.  The API of the method has been simplified
as well:

    @api.multi
    def _read_group_stage_ids(self, domain, read_group_order=None, access_rights_uid=None):
        # the stages are given by self.ids (wrong model);
        # read_group_order is the order given to read_group() on self;
        # return stages.name_get(), {stage.id: stage.fold)

    _group_by_full = {'stage_id': _read_group_stage_ids}

is now written:

    stage_id = fields.Many2one(..., group_expand='_read_group_stage_ids')

    @api.model
    def _read_group_stage_ids(self, stages, domain, order):
        # stages is a recordset;
        # order is the order to use on stages' model;
        # return a recordset which is a superset of stages

1 files changed, 9 insertions, 0 deletions

diff --git a/odoo/tools/sql.py b/odoo/tools/sql.py
index 43c54c1a28a..0c67657db8d 100644
--- a/odoo/tools/sql.py
+++ b/odoo/tools/sql.py
@@ -24,3 +24,12 @@ def pg_varchar(size=0):
         if size > 0:
             return 'VARCHAR(%d)' % size
     return 'VARCHAR'
+
+def reverse_order(order):
+    """ Reverse an ORDER BY clause """
+    items = []
+    for item in order.split(','):
+        item = item.lower().split()
+        direction = 'asc' if item[1:] == ['desc'] else 'desc'
+        items.append('%s %s' % (item[0], direction))
+    return ', '.join(items)