Build against semigroups-0.19 (#54)

Also drop support for GHC 7.6 since our dependencies no
longer support it

.travis.yml

@@ -13,9 +13,6 @@ before_cache:
 
 matrix:
   include:
-    - env: CABALVER=1.16 GHCVER=7.6.3
-      compiler: ": #GHC 7.6.3"
-      addons: {apt: {packages: [cabal-install-1.16,ghc-7.6.3], sources: [hvr-ghc]}}
     - env: CABALVER=1.18 GHCVER=7.8.4
       compiler: ": #GHC 7.8.4"
       addons: {apt: {packages: [cabal-install-1.18,ghc-7.8.4], sources: [hvr-ghc]}}

optparse-applicative.nix

@@ -1,15 +0,0 @@
-{ mkDerivation, ansi-wl-pprint, base, bytestring, process
-, QuickCheck, stdenv, transformers, transformers-compat
-}:
-mkDerivation {
-  pname = "optparse-applicative";
-  version = "0.14.0.0";
-  sha256 = "06iwp1qsq0gjhnhxwyhdhldwvhlgcik6lx5jxpbb40fispyk4nxm";
-  libraryHaskellDepends = [
-    ansi-wl-pprint base process transformers transformers-compat
-  ];
-  testHaskellDepends = [ base bytestring QuickCheck ];
-  homepage = "https://github.com/pcapriotti/optparse-applicative";
-  description = "Utilities and combinators for parsing command line options";
-  license = stdenv.lib.licenses.bsd3;
-}

optparse-generic.cabal

@@ -7,7 +7,7 @@ License-File: LICENSE
 Copyright: 2016 Gabriel Gonzalez
 Author: Gabriel Gonzalez
 Maintainer: Gabriel439@gmail.com
-Tested-With: GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1
+Tested-With: GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1
 Bug-Reports: https://github.com/Gabriel439/Haskell-Optparse-Generic-Library/issues
 Synopsis: Auto-generate a command-line parser for your datatype
 Description: This library auto-generates an @optparse-applicative@-compatible
@@ -33,7 +33,7 @@ Library
         time                 >= 1.5      && < 1.9 ,
         void                                < 0.8 ,
         bytestring                          < 0.11,
-        semigroups           >= 0.5.0    && < 0.19
+        semigroups           >= 0.5.0    && < 0.20
 
     if impl(ghc < 7.8)
         Build-Depends:

release.nix

@@ -13,16 +13,19 @@ let
     packageOverrides = pkgs: {
       haskellPackages = pkgs.haskellPackages.override {
         overrides = haskellPackagesNew: haskellPackagesOld: {
-          optparse-applicative = haskellPackagesNew.callPackage ./optparse-applicative.nix { };
-
           optparse-generic = haskellPackagesNew.callPackage ./default.nix { };
         };
       };
     };
   };
 
-  pkgs =
-    import <nixpkgs> { inherit config; };
+  nixpkgs = builtins.fetchTarball {
+    url = "https://github.com/NixOs/nixpkgs/archive/312a059bef8b29b4db4e73dc02ff441cab7bb26d.tar.gz";
+
+    sha256 = "1j52yvkhw1inp6ilpqy81xv1bbwgwqjn0v9647whampkqgn6dxhk";
+  };
+
+  pkgs = import nixpkgs { inherit config; };
 
 in
   { optparse-generic = pkgs.haskellPackages.optparse-generic;