bundle2: merge return values when bundle contains multiple changegroups A bundle2 may contain multiple parts adding changegroups, in which case there are multiple operation records for changegroups, each with its own return value. Those multiple return values are aggregated in a single cgresult value for the whole operation. As can be seen in the associated test case, the situation with hooks is not really the best, but without deeper thoughts and changes, we can't do much better. Hopefully, things will be improved before bundle2 is enabled by default. In the meanwhile, multiple changegroups is not expected to be in widespread use, and even less expected to be used for pushes. Also, not many clients cloning or pulling bundle2 with multiple changesets are not expected to have changegroup hooks anyways.