Switch from svn to git and modify repo completely

[Matthias Fechner <idefix@fechner.net>]

Dear Git List,

I just started to migrate a svn repo to a git repo and was successfully
with the "git svn" command and waiting a long time :)

I have now some confidential documents in the repository I must remove
completely (including the complete history). These are single files
spread over the complete repository. Is this possible with git?

The next step I would like to do is separate the repo and smaller ones.
The problem here is it is not only take this directory and move it out,
it is a complete mess and the files are spread over the complete repo
and over all the revisions (files were moved around in the old
subversion repo from folder to folder). Is there a possibility to say
take file1, file2, fileN and directory1, directoryN and move it to
another repo or remove all not matching files/directories completely?

Thanks a lot for some hints which commands I could use here or if it is
possible.

Bye
Matthias