EMF Compare/Restrict comparison on selection
In the tree comparison editor, a right click on an DiffGroup MUST open a popup menu. It gives the ability to select the selected element as the new root of the comparison. Then, the StructureMergeViewer is updated to only show the differences below the selected element.
As soon as a DiffGroup has been selected to restrict the comparison, the popup menu does not allow to select a new DiffGroup to further restrict the comparison but only to restore the whole comparision view.