If you integrate changes in a sibling stream (rather than in a parent stream,
you can use an alternate target deliver operation to share changes between
sibling streams. For example, if you deliver activities b1, b2,
and b3 in stream D2 to stream D1, you must also deliver
activities in baselines in PA.BL1 and merge the changes with the versions
in activities a1, a2, and a3. This complex deliver operation
can be simplified by using a rebase operation before the alternate target
deliver operation.
All of the integrated changes are migrated to the parent stream (the project
integration stream) when you deliver your work from stream D1.