[442897] Pseudo conflicts under Real Add conflicts

Pseudo conflicts under Real Add conflicts must be detected as Real
conflicts, because pseudo conflicts are equivalent. But under a real add
conflict, we must have the possibility to merge a diff separately.

Bug: 442897
Change-Id: Id72634cdefa65698e82fc0aab9f227bb88915e24
Signed-off-by: Axel Richard <axel.richard@obeo.fr>