rebase: rebase changesets in topo order (issue5370) (BC) There are two reasons that rebase should be done this way: 1. This would make rebasing faster because it would minimize the total number of files to be checked out in the process, as it don't need to switch back and forth between branches. 2. It makes resolving conflicts easier as user has a better context. This commit changes the behavior in "Test multiple root handling" of test-rebase-obsolete.t. It is an expected change which reflects the new behavior that commits in a branch are grouped together when rebased.