Revision rights by content type
I needed to allow revision viewing and reverting (but not deleting) for only one content type (a wiki). The solution turned out to be in hook_menu and module weights, and overriding Drupal's menu structure for the revisions of wikis.
Basically another set of paths is created that read node/$nid/wiki-revision/$vid and all callbacks for wiki content types flow through newly defined callbacks. They're mostly cribbed from node.module, but have an additional OR permission of
user_access('edit wiki content'). Permission to delete revisions stays with
user_access('administer nodes'). The modules also depends on having a lighter system weight than
The complete module is attached below.