Removing part of the history

[Samuel Lucas Vaz de Mello <samuellucas@datacom.ind.br>]

Hi All,

I have a repository with code imported from CVS.

I first imported from CVS using git 1.5.6 and we started to develop in git branches.
I run cvsimport periodically and merged the changes from CVS (legacy developers) to our git branches.
After some time, I realized that the import was broken, upgraded to git 1.6 and reimported the data.
Now the imported data seems to be correct and I finished with a history tree like this:

(our branch1)             X--Y--Z
merges>                  /    \
(our branch2)       J--K--L--M--N--O--P
merges>             /     /     /
(cvs old) ...A--B--C--D--E     /
merges>                       /
(cvs new) ...A'-B'-C'-D'-E'-F'


There is any way to get rid of the (broken) cvs-old tree?

I've tried to rebase, but the commits from A' and A are different, it tries to reapply all history in CVS.

I've tried to checkout a point before our changes start (B') and then, using a script, cherry-pick all commits up to HEAD that are not in cvs-old branch. This approach didn't handled well merges between our branches (K-L-M and X-Y).

The history from the beginning up to the point where our changes started (...A--B) is quite large, so it would be nice for us to get rid of it. 

Any suggestion on how to handle this?

Thank you,

 - Samuel