Create offline haddocks including all dependencies, with an index

I am about to embark on a flight, and I was expecting that a call like

cabal new-haddock

would build the haddock of my current project and all its dependencies (which may not have haddocks yet), and also create a nice index akin to file:///usr/share/doc/ghc-doc/html/libraries/index.html with the haddocks of all visible packages. But it seems that this is not yet supported.

(I am not sure if #3535 is about this, or merely about a technical detail on the road to this feature.)