tests: add one more test case about handling of phase-divergence by evolve This patch adds a test case when phasedivergence is caused by rebase command and there is parent change involved. As the tests show, we are not handling things correctly here. Upcoming patches will fix that. Fixing things in later patches showed there was a wrong case in one another test which will be fixed by later patches, so let's add description on why that test is wrong in this patch.