Module that allows to compare, edit and/or merge revisions At the moment I have installed on my site the Diff module, which allows me to compare the content of 2 revisions but I need a module that allows me to not only see the differences between revisions, but also to edit both revisions at the same time while comparing them and to copy the content of a field to either revision (like WinMerge or many other diff/compare applications)

I am well aware that revisions shouldn't be used this way, but i'm using the revisions system to allow unregistered users to post edit suggestions about my site's content so being able to copy only certain fields (since a suggestion might include both correct and incorrect data for different fields) in the current revision would save me a lot of time
I doubt there is an out of the box solution. But maybe you can Views of Pending revision items per content item using Views and if needed the Revisioning module and maybe Rules. Eg, somehow you want to list stuff with pending changes and Revisioning+Rules seems to be able to do that:


  Rules: when Triggers won't do, use the event-condition-action paradigm
  of Rules. More complicated to set up than Trigger, but very powerful.
  Revisioning adds its own events and conditions to Rules, for example
  "content is about to be published" and "content has pending
  revisions".


Then for the view itself you could try to link to a 2nd page that uses the Diff Different module to make the UI per field item you are talking about to move field data around.

I don't see any out of the box solution and you need to build a Workflow of pages/forms/views etc. I'm just trying to help by listing some tools to help achieve that.