Re: How to populate index/worktree when recursive merge merges multiple common ancestors?

They don't. The conflicts are preserved into the virtual ancestor. The
user only sees the final conflicts during merging of A and B with
virtual X3 as the common ancestor.

Ah, now I understand. When I merge X1 and X2 into the virtual X3
I should not stop if this is not doable without conflict resolution. I
should store in memory the X3 content, including all the conflict
markers. If I finally merge A and B I will specify a common base
content which may contain conflict markers. Right?
Are git config param's like merge.conflictstyle=diff3 are also
effective when creating the virtual X3 content? Couldn't that lead to
complicated conflict marker situations? In the area where you expect
common base content you again see conflict markers in diff3 style.