I've also done some archaeology and found that the original version of
the merge preserving code was written by Johannes Schindelin
<johannes.schinde...@gmx.de>, see e.g.
There were also some big discussion threads in 2007-2008 regarding a
better mechanism to "mark" or "tag" the heads of rebased branches, but I
haven't seen consensus and development in that direction after that.
PS There are also some pieces of "what should work" in these tests:
Mit freundlichen Grüßen,