Thanks @anon41087856 , just what I needed. Have successfully built, and here is my first effort with it, a Banksy in Bristol UK with recently added (and hopefully eventually will be removed) mask. I will need to get to grips with the new controls of course.
Thanks for filmic and the continued development.
One thing I noticed in this build, not obviously related to filmic, is that previously if I selected an image in lighttable and double-clicked a style, it would be applied immediately. Now it is not applied until I go into darktable. But it does remain applied when going back to lighttable.