obsolete: allow multiple predecessors in createmarkers...
obsolete: allow multiple predecessors in createmarkers
The logic for this change is similar to the change to `cleanupnodes` that we
did earlier. Now that the rebase code is trying to record a fold, we need to
actually record it in the markers. The first step is to have the markers
creation API able to receive such fold data.
To keep things sane, we restrict fold to on successors.