- The types are:
-- Previous: The default and the previously used type
-- Subsequent: Compares against the next version
-- Current: Compares against the current version
- Allow switching between comparison types in index and diff views
-- Have links vary depending upon current comparison type
* Factor out common sidebar layout template.
* Convert wiki pages and posts to use this template.
* Add data-layout attribute to <body> element indicating the current layout.
Changes to the /wiki_page_versions global listing:
* Add "diff" links that show you what changed in the given edit.
* Add "?" links that take you to the current version of the wiki.
* Add "»" links next to wiki page titles that take you to the wiki's full edit history.
* Add "»" links next to usernames that take you to the user's full edit history.
* Add a "Status" column that shows whether the wiki page was created,
deleted, undeleted, or renamed.
* Link to /wiki_page_versions in sidebar, not /wiki_pages?order=time.
Split the wiki page versions template into two partials,
_global_listing.html.erb and _page_listing.html.erb, to avoid the nested
conditionals that arise from combining these two pages into one template.
Add html IDs to distinguish between these two partials.
