Rebasing multiple branches

[Leonid Podolny <leonidp.lists@gmail.com>]

Hi,
I need to rebase a rather complicated formation of branches.

My situation is like this (I hope ASCII graphics survive the sending):

         B--o--o--o--o--o--o  <--branch A
        /                   \
o--o--A--o--E  <--master    C--o--o--o--D  <--branch C
        \                   /
         C--o--o--o--o--o--o  <--branch B

I would like to rebase all three branches A, B and C onto commit E, and 
it's very important to keep the information about merges. For instance, 
if I take commit C and rebase it onto D, it serializes all the 
intermediate commits.
The only solution I managed to come up with is as follows:
- Take branch A and rebase it onto D (branch A').
- Same with branch B.
- Open a new branch C' from commit E.
- Merge A' and B' into C'.
- Manually cherry-pick all commits from commit C to commit D into branch C'.


The last step is way too ugly to be the only possible solution :)