evolve: refactor the code which swap two nodes (in divergence resolution)
I see that we are using the code to swap the "divergent" and "other" node;
and updating the evolvestate accordingly at many places in divergence
resolution. This patch extract that code to a function.
Although I don't have strong opinion on this patch. It's a volunteered
patch to remove some redundancy.
evolve: remove tmpctx arg from _resolvephasedivergent()
Before this patch, in _resolvephasedivergent() function we were passing
an optional argument "tmpctx" which was used to store a rebased version
of bumped if required. But for sake of simplicity we can achieve the
same results even without passing this "tmpctx" into that function.
No changes in test files demonstrate that this patch don't break
anything.