Hi Laurent,
I assume you are referring to moving the contents of Opal's wiki[1] to Eclipse? If so, I suspect the correct destination for all of it is Nebula's website [2] rather than the Eclipse wiki. The Nebula website is in its own git repo [4] which you should have access to as a committer (once paperwork has gone through).
As you already have a good quality Wiki I wonder if there are some offline tools that can be used to generate HTML from the markdown in your existing wiki, and store both the wiki and the generated HTML in the website git. That would allow the editing of the pages to remain in a markdown format and integrate with the Nebula website. Github has a RESTful [5] API that supports github flavoured markdown that you may have used in the existing wiki. There is also Jekyll[6].
If you want to migrate, you could covert all your documentation to the php style used already on the Nebula website.
I don't know if this goes beyond the scope of what you were looking for or properly answers your questions, but hopefully it is a good start to the conversation.
HTH,
Jonah
