Add test for basename in #extract_nestedly.

Library/Homebrew/test/unpack_strategy_spec.rb

@@ -56,6 +56,23 @@
         expect(Pathname.glob(unpack_dir/"**/*")).to include unpack_dir/directories
       end
     end
+
+    context "when extracting a nested archive" do
+      let(:basename) { "file.xyz" }
+      let(:path) {
+        (mktmpdir/basename).tap do |path|
+          mktmpdir do |dir|
+            FileUtils.touch dir/"file.txt"
+            system "tar", "-c", "-f", path, "-C", dir, "file.txt"
+          end
+        end
+      }
+
+      it "does not pass down the basename of the archive" do
+        strategy.extract_nestedly(to: unpack_dir, basename: basename)
+        expect(unpack_dir/"file.txt").to be_a_file
+      end
+    end
   end
 end
 

Library/Homebrew/unpack_strategy.rb

@@ -197,18 +197,18 @@ def self.can_extract?(path:, magic_number:)
   def extract_to_dir(unpack_dir, basename:)
     super
     safe_system Formula["xz"].opt_bin/"unxz", "-q", "-T0", unpack_dir/basename
-    extract_nested_tar(unpack_dir, basename: basename)
+    extract_nested_tar(unpack_dir)
   end
 
-  def extract_nested_tar(unpack_dir, basename:)
+  def extract_nested_tar(unpack_dir)
     return unless DependencyCollector.tar_needs_xz_dependency?
     return if (children = unpack_dir.children).count != 1
     return if (tar = children.first).extname != ".tar"
 
     Dir.mktmpdir do |tmpdir|
       tmpdir = Pathname(tmpdir)
       FileUtils.mv tar, tmpdir/tar.basename
-      TarUnpackStrategy.new(tmpdir/tar.basename).extract(to: unpack_dir, basename: basename)
+      TarUnpackStrategy.new(tmpdir/tar.basename).extract(to: unpack_dir)
     end
   end
 end