FIX: change title when primary group changes (#6602)

app/models/group_user.rb

@@ -24,14 +24,7 @@ class GroupUser < ActiveRecord::Base
   end
 
   def set_primary_group
-    if group.primary_group
-      DB.exec("
-        UPDATE users
-        SET primary_group_id = :id
-        WHERE id = :user_id",
-        id: group.id, user_id: user_id
-      )
-    end
+    user.update!(primary_group: group) if group.primary_group
   end
 
   def remove_primary_group

spec/models/group_spec.rb

@@ -710,11 +710,16 @@ describe Group do
     end
 
     it "always sets user's primary group" do
-      group.update(primary_group: true)
+      group.update(primary_group: true, title: 'AAAA')
       expect { group.add(user) }.to change { user.reload.primary_group }.from(nil).to(group)
 
-      new_group = Fabricate(:group, primary_group: true)
-      expect { new_group.add(user) }.to change { user.reload.primary_group }.from(group).to(new_group)
+      new_group = Fabricate(:group, primary_group: true, title: 'BBBB')
+
+      expect {
+        new_group.add(user)
+        user.reload
+      }.to change { user.primary_group }.from(group).to(new_group)
+        .and change { user.title }.from('AAAA').to('BBBB')
     end
 
     context 'when adding a user into a public group' do