With hte manuals described in index.txt ronn will create hyperlinks of the (1) referenced words.
See http://rtomayko.github.com/ronn/ronn.1#LINK-INDEXES.
git-extras.html will now be browsable, actually anywhere else you use the referenced names ie. git-extras(1) as defined in index.txt will generate as hyperlinks in html while keeping the text versions rendereder similarly than they used to using exactly the same procedures as already documented.