Managing sub-projects

[Michael Eager <eager@eagerm.com>]

I'm trying to create a git repository for a tool chain for a proprietary
processor.  I'd like to create a private repo with documentation, build
scripts, etc., which includes several sub-projects: binutils, gcc, newlib,
etc.  Each of the sub-projects will have a branch which has support for
the new processor.  These branches need to be maintained in my repo, not
in the upstream repo.  I want to be able to periodically rebase these
branches from the upstream repo.

I've looked at several schemes, but each one seems to do something other
than what I want.

Git submodule:  Branches created in the sub-projects are pushed to the
upstream repo, not to my repo.  I tried to change origin and created an
upstream reference, but was not able to get changes pushed to my repo.

git subtree:  Does not maintain sub-project history or allow rebase.

git slave:  Requires multiple private repos.  Appears to require the
same branch names in each sub-project.

repo: Appears to work a bit like git submodules, where pushes on the
sub-projects go to the upstream repo, not to the private repo.

Any other ways to do what I want without creating a separate forked
repo for each of the sub-projects?  Or have I misunderstood one of
these schemes?

-- 
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077