Backing Out a backwards merge on Mercurial

Question

How do you reverse the effect of a merge on polarised branches without dying of agony?

This problem has been plaguing me for months and I have final

Answer 1

After much discussion with some of the helpful people on #mercurial on freenode, mpm has provided a partial solution that seems to work for my test case ( I generated a fake repository trying to replicate the scenario )

However, on my actual repository, for reasons I don't quite understand, it is still less than perfect.

Here is a diagram of the currently proposed way of resolving this problem:

[Original image lost]

Its now less of a problem to fix, but I'm still having to compare diffs ( ie: b46:b11 vs b46:b8 , a43:a10 vs a43:a9 ) and hand edit some changes back in.

Not closing this question/taking an answer until I get a guaranteed way that works on any repository.

Important

Anyone trying this stuff should clone their repository and play with it like a sandbox first. As you should be doing with any merge process, because that way if it goes wrong you can just throw it out and start again.