Workflow for templates?

Hello everybody,

I am looking for a setup where teplates can be handled easily.

For a better explanation of what I'm trying to achieve, I use the apache httpd project as an example.

Apache httpd provides an extensively commented httpd.conf template, which users can use as a starting point for their own customization.

Tha's fine so far. But I'd like this to work in both directions:

Downstream: When the upstream template has new changes, I can merge them into
my local branch. Conflicts will remind me that I have to review my
customization.

Upstream: Within the customized working copy, I implement a new module or
change an existing one (e.g. mod_ssl). While implementing the new feature, I
add/modify my _customized_ template. When I'm happy with the new feature, I'd
like to rewrite the localized customization into something generic and send it
along with the implementation of the new feature to the upstream generic
template. My localized customization should not get lost during the
process, of course.

One more important aspect: since the customized template might contain confidential information, those bits should have a hard time to propagate to the upstream repository.

I guess the downstream part can be done by a vendor branch. But I have a hard time to find a proper workflow for the upstream part.

Any ideas?