[470503] Some cascading diffs not merged with menu/merge actions

Cascading diff was not taking into account with the contextual menu.
It was also not taking into account by the merge right to left / left to
right actions.
Add new test case.

Change-Id: I1cd7bf15359c875ded35585e56d253d7db2f4617
Signed-off-by: Axel Richard <axel.richard@obeo.fr>
7 files changed