Mercurial - backout an old merge

Question

I have a branch that looks like this:

A->B->C->D->...->Z
     ^
1->2-^

where C is a merge from 2 an

Answer 1

A little bit late, but I had the same situation a while ago. This worked for me smoothly:

hg update -C -r "revision-C"
hg revert --all -r "revision-B"
hg commit -m 'UNDO blah blah whatever the merge did'
hg update -C -r "revision-Z-or-whatever-the-current-head-is"
hg merge -r "the-new-revision-created-in-step-3"

Basically, this is exactly what backout does.

DISCLAIMER: Please note however that if you later in the future want to merge the 1->2 branch again, you will most probably run into some issues. And "some issues" is a somewhat euphemestic term here. In fact, even BIG PROBLEMS may appear in such a case. This scenario is dangerous mainly because the problems may arise much later and totally unexpected. It is highly recommended to abandon the "1" branch completely to avoid these risks. (Also see the comments below.)

For details, see Backout wiki page.