#1 Tags deleted when cascading conflicts

[Muriel Salvan]

When cascading conflicts into a cycle, Tags end up all deleted.

1. Rename a Tag getting conflict into another one: conflict dialog appears
2. Rename it in the conflict dialog to make it conflict with a third one, choose to merge using new values: a second conflict dialog appears
3. Rename it in the conflict dialog to make it conflict again with the first one, choose to merge using new values: a third conflict dialog appears
4. Merge using new values. The 3 Tags will be deleted.