tests: demonstrate crash when trying to rebase merge without its parents As the test case shows, when "hg rebase -d G -r 'B + D + F'" is run on the following graph, we crash with traceback. It's reasonable to fail because we can not easily produce a correct rebased F. The problem is what diff to apply to either the rebased B or the rebased D. We could potentially produce the result by e.g. applying the (F-D) diff to the rebased B and then applying the reverse (E-D) diff on top, but that could result in merge conflicts in each of those steps, which we don't have a way of dealing with. So for now, let's just add a test case to demonstrate that we crash (i.e. the AssertionError is clearly incorrect since the user can run into it). F /| C E | | B D G \|/ A Differential Revision: https://phab.mercurial-scm.org/D212