Honoring changed target branch on rebase

You are able to change the target branch for pull requests on Github and when dependabot rebases the PR it defaults back to the original branch. It would be great if dependabot honors the changed target branch for rebase etc. as it would come in usefull for major updates in dependencies. For example the recent angular 8 launch caused 10+ dependencies to be updated for a project all at once with breaking changes on some projects coming from angular 7.
I created a angular 8 migration branch for test purposes and it would be great if you could redirect those Dependency PRs from dependabot this way to another branch without manual merging.

Have a nice day and thanks a lot for a great product!

No file, test, or entry point is named in the issue. Start by reproducing a Dependabot rebase after changing a pull request's target branch, then trace the rebase flow that selects the branch. Done means rebases preserve the changed target branch, including dependency updates redirected to a migration branch, with coverage for the reported Angular-style scenario.

Written by the indexing model from the issue text.