Bzr has a pipelines plug-in which does basically this. Branches can be stacked on top of each other forming a “pipeline”, and propagating changes from one branc

Bzr has a pipelines plug-in which does basically this. Branches can be stacked on top of each other forming a “pipeline”, and propagating changes from one branch to the dependent / subsequent ones is achieved with one command, “bzr pump”. Bzr has no concept of rebasing, so what you get is a simple merge, but with very little work on your part.