[Zope] Deploying with buildout (was: buildout, instancemanager, and eggs)

[Ross Patterson]

We have a Plone 3.0/Zope 2.10 application that we need to develop on, maintain and
deploy to a ZEO server and multiple ZEO clients.  Currently we use svn
bundles of Zope and Plone and our own packages and products in one big
svn:externals definition.  We also use some more recent versions of
certain products and packages than those included in the upstream
svn:externals.  For example:

Zope svn://svn.zope.org/repos/main/Zope/branches/2.10
Zope/lib/python/zope/app/interface svn://svn.zope.org/repos/main/zope.app.interface/trunk/src/zope/app/interface

Though I haven't seen any documentation to this effect, svn seems to
treat the second svn:externals as a "svn switch" on "svn up".

So one question I have is how would I "override" the versions of some
package like this using buildout?

Another question I have is that there aren't releases for all the
dependencies our application has.  I'm wondering what the best way is to
define a canonical release for deployment to our cluster.  Ideally, we'd
have a buildout (or whatever) on a staging server where we're testing
the candidate for deployment and then when all tests pass that *exact*
source should be deployed to the cluster.  How might one do this without
upstream releases?  Is there a way to get buildout and setuptools to
play together so that I can build a source distribution from the test
passing buildout on staging?  Is there a way I can have a buildout on
each cluster node such that a simple ./bin/buildout will get the latest
deployment release for that node?

Ross