Reapply "Actually ignore system/user registries during locking"

This reverts commit 3b5f0d9.

Author: edolstra

src/libflake/flakeref.cc

@@ -39,7 +39,7 @@ FlakeRef FlakeRef::resolve(
     ref<Store> store,
     const fetchers::RegistryFilter & filter) const
 {
-    auto [input2, extraAttrs] = lookupInRegistries(store, input);
+    auto [input2, extraAttrs] = lookupInRegistries(store, input, filter);
     return FlakeRef(std::move(input2), fetchers::maybeGetStrAttr(extraAttrs, "dir").value_or(subdir));
 }
 

tests/functional/flakes/flakes.sh

@@ -220,6 +220,13 @@ nix store gc
 nix registry list --flake-registry "file://$registry" --refresh | grepQuiet flake3
 mv "$registry.tmp" "$registry"
 
+# Ensure that locking ignores the user registry.
+mkdir -p "$TEST_HOME/.config/nix"
+ln -sfn "$registry" "$TEST_HOME/.config/nix/registry.json"
+nix flake metadata flake1
+expectStderr 1 nix flake update --flake-registry '' --flake "$flake3Dir" | grepQuiet "cannot find flake 'flake:flake1' in the flake registries"
+rm "$TEST_HOME/.config/nix/registry.json"
+
 # Test whether flakes are registered as GC roots for offline use.
 # FIXME: use tarballs rather than git.
 rm -rf "$TEST_HOME/.cache"