Use case: Be able to compare an existing wiki with an extension. For example compare my wiki with xwiki-enterprise-common-ui to see the differences I have in my wiki. Implementation idea: We could imagine an extra action in the EM UI: when listing an Extension, you can now Install/Remove/Upgrade. We could imagine a secondary option to "Compare". Clicking it would compare the extension with the current pages in the wiki, showing diffs for all pages contained in the extension vs pages on the wiki. For example if you pick the Blog UI, the "Compare" button would compare the blog app in the listed version with the current blog pages in the wiki. And if you select the xwiki-enterprise-common-ui extension it'll do the same but comparing a lot more pages. We could also imagine listing pages available in the wiki but not listed in the extension selected. WDYT? Real use case: I'd like to verify on xwiki.org wikis their state and what differences they have with the default "distribution". It would also be interesting and useful for us to verify the DW works well and doesn't do anything strange. And it would allow building trust with users. Subsidiary question: how hard would it be to implement this? Thanks -Vincent