Kelly F. Hickel, 05.06.2009:
Other than using manually format-patch on every branch in new,
then applying the patches (presumably with regular old patch, since the
ancestor commit IDs won't match), is there any "good" way to merge "new"
into "old"?
If rebasing 'new' on top of 'old' isn't an option, then you could try:
$ git checkout new
$ git merge -s ours old
It's the other way round (not merging 'new' into 'old', but vice versa),
but there is now merge strategy "theirs".
Markus