Make default.nix an overlay

[asymmetric]

Similar to mozilla-nixpkgs.

Benefits:

• familiarity (this is all you'd have to do), and then you could just add dapp or seth to home.packages or environment.systemPackages.
• makes more sense

Cons:

• Current users might have to change how they import the pkgset
• Do we break someone's workflow?

I think for this to actually work well, we'd have to stop exporting this, otherwise we're actually going to interfere with haskell dependencies from nixpkgs, which can cause lots of downstream rebuilds.

[MrChico]

Wrt the haskell stuff I think we need to update to latest ghc, which shouldnt be too hard

[livnev]

@asymmetric Won't something like this work already?

  overlays = [ (import (builtins.fetchGit {
    url = "git@github.com:dapphub/dapptools.git";
    rev = "4b45ad07bafd6917f4bf5ba518d53f0ad1f82de3";
    } + /overlay.nix)
  ];

[asymmetric]

@livnev yeah absolutely, but it’s one more thing we have to explain people how to do (or they have to figure out themselves).

The main benefit would be standardization.

[livnev]

@asymmetric Agreed. 👍

While we are on the subject, what is the advantage of the overlay approach versus doing something like

dapptools = import (builtins.fetchGit {
    url = "git@github.com:dapphub/dapptools.git";
    rev = "4b45ad07bafd6917f4bf5ba518d53f0ad1f82de3";
    }) {};

and then using dapptools.seth etc.? That way we know we won't mess up people's haskell package set etc.

[asymmetric]

Now that I think of it, we would actually lose the binary cache, since everyone would be layering the overlay on top of a different version of nixpkgs. I think that's why we do it the current way in the first place.

The mozilla-nixpkgs overlay downloads (I guess statically linked?) pre-compiled binaries from mozilla's cache, so they don't have this problem.

:thinking: