git-lfs: adding old 1.5.6 (supports old server protocols)

Some git-lfs servers may not be ready for 2.x clients.

pkgs/applications/version-management/git-lfs/1.nix

···
+{ stdenv, lib, buildGoPackage, fetchFromGitHub }:
+
+buildGoPackage rec {
+  name = "git-lfs-${version}";
+  version = "1.5.6";
+  rev = "0d02fb7d9a1c599bbf8c55e146e2845a908e04e0";
+  
+  goPackagePath = "github.com/git-lfs/git-lfs";
+
+  src = fetchFromGitHub {
+    inherit rev;
+    owner = "git-lfs";
+    repo = "git-lfs";
+    sha256 = "0wddry1lqjccf4522fvhx6grx8h57xsz17lkaf5aybnrgw677w3d";
+  };
+
+  # Tests fail with 'lfstest-gitserver.go:46: main redeclared in this block'
+  excludedPackages = [ "test" ];
+
+  preBuild = ''
+    pushd go/src/github.com/git-lfs/git-lfs
+      go generate ./commands
+    popd
+  '';
+
+  postInstall = ''
+    rm -v $bin/bin/{man,script}
+  '';
+  meta = with stdenv.lib; {
+    description = "Git extension for versioning large files";
+    homepage    = https://git-lfs.github.com/;
+    license     = [ licenses.mit ];
+    maintainers = [ maintainers.twey ];
+  };
+}

pkgs/top-level/all-packages.nix

···
 
   git-crecord = callPackage ../applications/version-management/git-crecord { };
 
-  git-lfs = callPackage ../applications/version-management/git-lfs { };
+  git-lfs = lowPrio (callPackage ../applications/version-management/git-lfs { });
+
+  git-lfs1 = callPackage ../applications/version-management/git-lfs/1.nix { };
 
   git-ftp = callPackage ../development/tools/git-ftp { };