Write access to the repository. Or the link between the repository and the other sections.
I think it would be cool if we could save some documents, such as wiki pages, into the repository.
Or, for example, update the TODO file, depending on the issues. Or, attach files from the section "documents" to the repository.
Once again, for example. If we changed the wiki page -> redmine created new commit. Or else, we have changed the file in the repository "doc / wiki / index.tl", and it was renewed in the "wiki" section.
It do not easy, but it is very cool.