Patch Set 4: I would prefer that you didn't submit this

I have a reproducable issue where a node was still shown in the <working tree> node after I staged it:

- I have two java classes in a package, A is dirty, B is staged
- Team > Synchronize Workspace
- Navigate to A with the button "Next Difference"
- Stage A by drag and drop on <staged changes>
- Press "Next Difference" again
-> A is shown in the <working tree>, but with the "staged" decorator 

To test it I had cherry-picked the change on top of d027e85309983b8da5307bbbf26057e89093dff5