Merge branch 'master' into staging-next

There ver very many conflicts, basically all due to
name -> pname+version.  Fortunately, almost everything was auto-resolved
by kdiff3, and for now I just fixed up a couple evaluation problems,
as verified by the tarball job.  There might be some fallback to these
conflicts, but I believe it should be minimal.

Hydra nixpkgs: ?compare=1538299

pkgs/tools/nix/nixpkgs-fmt/default.nix

@@ -0,0 +1,21 @@
+{ lib, rustPlatform, fetchFromGitHub }:
+rustPlatform.buildRustPackage rec {
+  pname = "nixpkgs-fmt";
+  version = "0.2.0";
+
+  src = fetchFromGitHub {
+    owner = "nix-community";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "0sa0263pkpi423f1rdyg90axw9sdmgj8ma1mza0v46qzkwynwgh3";
+  };
+
+  cargoSha256 = "0p3qa1asdvw2npav4281lzndjczrzac6fr8z4y61m7rbn363s8sa";
+
+  meta = with lib; {
+    description = "Nix code formatter for nixpkgs";
+    homepage = "https://nix-community.github.io/nixpkgs-fmt";
+    license = licenses.asl20;
+    maintainers = with maintainers; [ zimbatm ];
+  };
+}