cask install: fix APFS DMG eject to use physical disk

Library/Homebrew/test/cask/installer_spec.rb

@@ -16,13 +16,27 @@ describe Cask::Installer, :cask do
       expect(caffeine.config.appdir.join("Caffeine.app")).to be_a_directory
     end
 
-    it "works with dmg-based Casks" do
-      asset = Cask::CaskLoader.load(cask_path("container-dmg"))
+    [
+      ["HFS+", "container-dmg"],
+      ["APFS", "container-apfs-dmg"],
+    ].each do |filesystem, cask|
+      it "works with #{filesystem} dmg-based Casks" do
+        asset = Cask::CaskLoader.load(cask_path(cask))
+        diskutil_list_command = "diskutil list | grep '/dev'"
+
+        sleep(1)
+        original_diskutil_list = `#{diskutil_list_command}`
 
         described_class.new(asset).install
 
-      expect(Cask::Caskroom.path.join("container-dmg", asset.version)).to be_a_directory
+        expect(Cask::Caskroom.path.join(cask, asset.version)).to be_a_directory
         expect(asset.config.appdir.join("container")).to be_a_file
+
+        sleep(2)
+        expect { system diskutil_list_command }
+          .to output(original_diskutil_list)
+          .to_stdout_from_any_process
+      end
     end
 
     it "works with tar-gz-based Casks" do

Library/Homebrew/test/support/fixtures/cask/Casks/container-apfs-dmg.rb

@@ -0,0 +1,9 @@
+cask "container-apfs-dmg" do
+  version "1.2.3"
+  sha256 "0630aa1145e8c3fa77aeb6ec414fee35204e90f224d6d06cb23e18a4d6112a5d"
+
+  url "file://#{TEST_FIXTURE_DIR}/cask/container-apfs.dmg"
+  homepage "https://brew.sh/container-apfs-dmg"
+
+  app "container"
+end

Library/Homebrew/unpack_strategy/dmg.rb

@@ -87,10 +87,31 @@ module UnpackStrategy
         return unless path.exist?
 
         if tries > 1
+          disk_info = system_command!(
+            "diskutil",
+            args:         ["info", "-plist", path],
+            print_stderr: false,
+            verbose:      verbose,
+          )
+
+          # For HFS, just use <mount-path>
+          # For APFS, find the <physical-store> corresponding to <mount-path>
+          eject_paths = if disk_info.success?
+            disk_info.plist
+                     .fetch("APFSPhysicalStores", [])
+                     .map { |store| store["APFSPhysicalStore"] }
+                     .compact
+                     .presence || [path]
+          else
+            [path]
+          end
+
+          eject_paths.each do |eject_path|
             system_command! "diskutil",
-                          args:         ["eject", path],
+                            args:         ["eject", eject_path],
                             print_stderr: false,
                             verbose:      verbose
+          end
         else
           system_command! "diskutil",
                           args:         ["unmount", "force", path],