Per-site VS Global branches

Ok, we're discussing repos structure here. The question is, given Drupal's builtin per-site config dirs, are per-site SVN branches useful? It is possible, for instance, to put site-specific mods in the sites dir. Whether dev versions of mods which already exist in the global mods dir will consistently override the global copy, I don't know. Let's check… [opens editor] ^v^v^ Yes! (includes/bootstrap.inc function drupal_get_filename). So there would seem to be no reason to mainain seperate branches for each site. Awesome! The other thing is access control on the sites dirs. So we have two (or three) branches: prod, test, dev. In each branch we have implemented some acls so that you only get the site dir if you pass muster. That sounds hard. So maybe we store the sites in another repos path. Then you need to explicitly check out the site. And each site is ACLed. Frito pie!