cask: fix writability check backing up an artifact

Library/Homebrew/cask/artifact/moved.rb

@@ -114,7 +114,7 @@ module Cask
         source.dirname.mkpath
 
         # We need to preserve extended attributes between copies.
-        command.run!("/bin/cp", args: ["-pR", target, source], sudo: !target.parent.writable?)
+        command.run!("/bin/cp", args: ["-pR", target, source], sudo: !source.parent.writable?)
 
         delete(target, force: force, command: command, **options)
       end

Library/Homebrew/test/cask/artifact/app_spec.rb

@@ -263,6 +263,11 @@ describe Cask::Artifact::App, :cask do
   end
 
   describe "uninstall_phase" do
+    after do
+      FileUtils.chmod 0755, target_path if target_path.exist?
+      FileUtils.chmod 0755, source_path if source_path.exist?
+    end
+
     it "deletes managed apps" do
       install_phase
 
@@ -272,6 +277,16 @@ describe Cask::Artifact::App, :cask do
 
       expect(target_path).not_to exist
     end
+
+    it "backs up read-only managed apps" do
+      install_phase
+
+      FileUtils.chmod 0544, target_path
+
+      expect { uninstall_phase }.to raise_error(Errno::ENOTEMPTY)
+
+      expect(source_path).to be_a_directory
+    end
   end
 
   describe "summary" do