Ryan Anderson [off-list ref] writes:
I've written a tool that will take a single commit, add it as a parent
of another commit, and recreate the history above that second commit in
a fully compatible manner.
I think the procedure is reproducible, which is a very nice
property to have for a tool like this, but I am not sure what
you mean by "in a fully compatible manner". What are you
compatible with?
Also another rhetorical, tongue-in-cheek question. What is your
plan to ripple the graft through to update signed tags? ;-)