Revert "do default-feature unification in nix"

This reverts commit 8f24ac1f27.

This is no longer necessary since the set of all features is equal to
the set of default features.

nix/pkgs/default/default.nix

@@ -11,7 +11,6 @@
 
 # Options (keep sorted)
 , default-features ? true
-, all-features ? false
 , features ? []
 , profile ? "release"
 , version-extra ? inputs.self.shortRev
@@ -20,19 +19,7 @@
 }:
 
 let
-  # We perform default-feature unification in nix, because some of the dependencies
-  # on the nix side depend on feature values.
   cargoManifest = lib.importTOML "${inputs.self}/Cargo.toml";
-  allDefaultFeatures = cargoManifest.features.default;
-  allFeatures = lib.unique (
-    lib.remove "default" (lib.attrNames cargoManifest.features) ++
-    lib.attrNames
-      (lib.filterAttrs (_: dependency: dependency.optional or false)
-        cargoManifest.dependencies));
-  features' = lib.unique
-    (features ++
-      lib.optionals default-features allDefaultFeatures ++
-      lib.optionals all-features allFeatures);
 
   buildDepsOnlyEnv =
     {
@@ -104,10 +91,13 @@ craneLib.buildPackage (commonAttrs // {
     env = buildDepsOnlyEnv;
   });
 
-  cargoExtraArgs = "--locked --no-default-features "
+  cargoExtraArgs = "--locked "
     + lib.optionalString
-      (features' != [])
-      "--features " + (builtins.concatStringsSep "," features');
+      (!default-features)
+      "--no-default-features "
+    + lib.optionalString
+      (features != [])
+      "--features " + (builtins.concatStringsSep "," features);
 
   env = buildPackageEnv;