How to maintain multiple branches (sid/bpo/exp etc)?

[Sandro Tosi <morph@debian.org>]

hello,
with the new DPMT repo layout and tools, what is the right way to
maintain multiple active branches for our packages? things like:

1. unstable at v(ersion)3, bpo70 at v1 and bpo8 at v2
2. unstable at v1, experimental at v2

all of them active, so in the 2. case there should be a way to keep
updating v1 and v2 releases (and so unstable and exp) as the come.

Thanks for your help,
-- 
Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi