[boost] [git][iostreams] Forking without an established merge point

If I look at the develop branch of Boost.Iostreams then GitHub says that "This branch is 253 commits ahead and 91 commits behind master". It appears that Boost.Iostreams has not established a merge point between master and develop as described in: https://svn.boost.org/trac/boost/wiki/PostCvtMergePoint I am trying to fork Boost.Iostreams to create some patches for it. Normally I would need to work off the develop branch (or a branch originating from develop), but if I do so my pull-requests will include the entire commit history of the component. If I look at the network graph of Iostreams, it appears that everybody else branches off the master branch. How do I proceed?