[IMP] runbot_merge: support for merging partners w/ github_login

The logic of the partner merge wizard is to collect all relevant data
from source partners, write them to a destination partner, then remove
the sources.

This... doesn't work when the field in question has a UNIQUE
constraint (like github_login), because it's going to copy the value
from a source onto a dest which will blow the constraint, and so the
copy fails. In that case the user first has to *move over* the unique
field's value then they can use the wizard.

Just fix for the github login: take all sources, remove (and store)
their github logins, then write the login onto the dst.

An alternative would have been to *defer* the constraint, however:

* it only works on unique constraints, not unique indexes
* it requires the constraint to be declared DEFERRABLE

Closes #301

conftest.py

@@ -1063,6 +1063,10 @@ class Model:
 
         return val
 
+    # because it's difficult to discriminate between methods and fields
+    def _call(self, name, *args, **kwargs):
+        return self._env(self._model, name, self._ids, *args, **kwargs)
+
     def __setattr__(self, fieldname, value):
         assert self._fields[fieldname]['type'] not in ('many2one', 'one2many', 'many2many')
         self._env(self._model, 'write', self._ids, {fieldname: value})

runbot_merge/models/res_partner.py

@@ -31,6 +31,22 @@ class Partner(models.Model):
                 email = ''
             partner.formatted_email = '%s <%s>' % (partner.name, email)
 
+class PartnerMerge(models.TransientModel):
+    _inherit = 'base.partner.merge.automatic.wizard'
+
+    @api.model
+    def _update_values(self, src_partners, dst_partner):
+        # sift down through src partners, removing all github_login and keeping
+        # the last one
+        new_login = None
+        for p in src_partners:
+            new_login = p.github_login or new_login
+        if new_login:
+            src_partners.write({'github_login': False})
+        if new_login and not dst_partner.github_login:
+            dst_partner.github_login = new_login
+        super()._update_values(src_partners, dst_partner)
+
 class ReviewRights(models.Model):
     _name = 'res.partner.review'
     _description = "mapping of review rights between partners and repos"

runbot_merge/tests/test_oddities.py

@@ -0,0 +1,22 @@
+def test_partner_merge(env):
+    p_src = env['res.partner'].create({
+        'name': 'kfhsf',
+        'github_login': 'tyu'
+    }) |  env['res.partner'].create({
+        'name': "xxx",
+        'github_login': 'xxx'
+    })
+    # proper login with useful info
+    p_dest = env['res.partner'].create({
+        'name': 'Partner P. Partnersson',
+        'github_login': ''
+    })
+
+    env['base.partner.merge.automatic.wizard'].create({
+        'state': 'selection',
+        'partner_ids': (p_src + p_dest).ids,
+        'dst_partner_id': p_dest.id,
+    })._call('action_merge')
+    assert not p_src.exists()
+    assert p_dest.name == 'Partner P. Partnersson'
+    assert p_dest.github_login == 'xxx'