combining repos

[j w]

Hello - I'm a mercurial newb, but haven't found an answer to this
question on the web or in archives.

Suppose I have two repos, A and B.
Now suppose I want to re-organize my directories somewhat, and as a
result, I want B to be a subdirectory of A.
So in the end I want one repo, A, which has subdir A/B containing
everything from the old B.
Of course, I want to maintain all history of B.

I know about "bundle" but you can't unbundle to a subdirectory, to my knowledge.
I also know about the forest extension, but that maintains the repos
separately. You have to remember to use 'fclone', etc. for certain
operations. I really want to "flatten" my two repos down to one, but
maintaining/combining the history of both.

Is there any way to do this - doesn't matter if it's archaic, I only
plan to do it rarely.

These posts seemed relevant, but didn't get much response:
http://selenic.com/pipermail/mercurial/2007-November/015724.html
http://selenic.com/pipermail/mercurial/2007-October/015294.html

Thanks
-John