override dual-tree

diagrams/dual-tree#13

nix/haskell/overrides.nix

@@ -2,6 +2,7 @@ self: super: {
 
 aeson-optics = self.callPackage (import ./overrides/aeson-optics.nix) {};
 dsv = self.callPackage (import ./overrides/dsv.nix) {};
+dual-tree = self.callPackage (import ./overrides/dual-tree.nix) {};
 grab = self.callPackage (import ./overrides/grab.nix) {};
 grab-form = self.callPackage (import ./overrides/grab-form.nix) {};
 hs-nix-modules = self.callPackage (import ./overrides/hs-nix-modules.nix) {};

nix/haskell/overrides/dual-tree.nix

@@ -0,0 +1,21 @@
+{ mkDerivation, base, fetchgit, monoid-extras, newtype-generics
+, QuickCheck, semigroups, stdenv, testing-feat
+}:
+mkDerivation {
+  pname = "dual-tree";
+  version = "0.2.2.1";
+  src = fetchgit {
+    url = "https://github.com/chris-martin/dual-tree.git";
+    sha256 = "1xlxr248sjvh6yv2nswivdg4qsm5530i8dp0h2pzqpxns04inqg9";
+    rev = "f8bfbe9226f277004ac8a3af781175ad8207684f";
+    fetchSubmodules = true;
+  };
+  libraryHaskellDepends = [
+    base monoid-extras newtype-generics semigroups
+  ];
+  testHaskellDepends = [
+    base monoid-extras QuickCheck semigroups testing-feat
+  ];
+  description = "Rose trees with cached and accumulating monoidal annotations";
+  license = stdenv.lib.licenses.bsd3;
+}