Support GPG (signed data) container in Homebrew Cask

Library/Homebrew/cask/lib/hbc/container.rb

@@ -6,6 +6,7 @@ require "hbc/container/criteria"
 require "hbc/container/dmg"
 require "hbc/container/executable"
 require "hbc/container/generic_unar"
+require "hbc/container/gpg"
 require "hbc/container/gzip"
 require "hbc/container/lzma"
 require "hbc/container/naked"
@@ -40,6 +41,7 @@ module Hbc
         Gzip,  # pure gzip
         Lzma,  # pure lzma
         Xz,    # pure xz
+        Gpg,   # GnuPG signed data
         Executable,
       ]
       # for explicit use only (never autodetected):

Library/Homebrew/cask/lib/hbc/container/gpg.rb

@@ -0,0 +1,41 @@
+require "tmpdir"
+
+require "hbc/container/base"
+
+module Hbc
+  class Container
+    class Gpg < Base
+      def self.me?(criteria)
+        criteria.extension(/GPG/n)
+      end
+
+      def import_key
+        if @cask.gpg.nil?
+          raise CaskError, "Expected to find gpg public key in formula. Cask '#{@cask}' must add: key_id or key_url"
+        end
+
+        args = if @cask.gpg.key_id
+          ["--recv-keys", @cask.gpg.key_id]
+        elsif @cask.gpg.key_url
+          ["--fetch-key", @cask.gpg.key_url.to_s]
+        end
+
+        @command.run!("gpg", args: args)
+      end
+
+      def extract
+        if (gpg = which("gpg")).nil?
+          raise CaskError, "Expected to find gpg executable. Cask '#{@cask}' must add: depends_on formula: 'gpg'"
+        end
+
+        import_key
+
+        Dir.mktmpdir do |unpack_dir|
+          @command.run!(gpg, args: ["--batch", "--yes", "--output", Pathname(unpack_dir).join(File.basename(@path.basename)), "--decrypt", @path])
+
+          extract_nested_inside(unpack_dir)
+        end
+      end
+    end
+  end
+end