git-subtree Next Round Ready

Ok, I've cleaned things up with git-subtree so the changes I had to the
test infrastructure are gone.  No changes to upstream are needed to
support git-subtree in contrib/ now.

As usual, the branches are here:

git://sources.obbligato.org/git/git.git

gitweb here: http://sources.obbligato.org/?p=git.git;a=summary

There are three branches.  master is the usual.  "subtree-latest" is my
version of git-subtree cleaned up for upstreaming into contrib/.  This
is the pure git-subtree history, ready to be subtree merged.
"subtree-integrated" is a version of upstream git.git with
subtree-latest merged as a subtree (done via git-subtree!).

I assume it will be easier to have Junio or another integrator do the
subtree merge from subtree-latest in his or her workarea but I provide
subtree-integrated so everyone can easily check out what it will look
like.

Let me know of anything else you need.

Thanks!

                         -Dave