move cabv method out of Pathname monkeypatch

recast as utility method

lib/cask/cli/info.rb

@@ -16,7 +16,7 @@ class Cask::CLI::Info < Cask::CLI::Base
 
   def self.info(cask)
     installation = if cask.installed?
-                     "#{cask.staged_path} (#{cask.staged_path.cabv})"
+                     "#{cask.staged_path} (#{Cask::Utils.cabv(cask.staged_path)})"
                    else
                      "Not installed"
                    end

lib/cask/installer.rb

@@ -75,7 +75,7 @@ class Cask::Installer
     else
       "#{Tty.blue.bold}==>#{Tty.white} Success!#{Tty.reset} "
     end
-    s << "#{@cask} staged at '#{@cask.staged_path}' (#{@cask.staged_path.cabv})"
+    s << "#{@cask} staged at '#{@cask.staged_path}' (#{Cask::Utils.cabv(@cask.staged_path)})"
   end
 
   def download

lib/cask/utils.rb

@@ -40,22 +40,6 @@ class Hash
   end
 end
 
-# monkeypatch Pathname
-class Pathname
-  # our own version of Homebrew's abv, with better defenses
-  # against unusual filenames
-  def cabv
-    out=''
-    n = Cask::SystemCommand.run!('/usr/bin/find',
-                                 :args => [self.realpath, *%w[-type f ! -name .DS_Store]],
-                                 :print_stderr => false).stdout.count("\n")
-    out << "#{n} files, " if n > 1
-    out << Cask::SystemCommand.run!('/usr/bin/du',
-                                    :args => ['-hs', '--', self.to_s],
-                                    :print_stderr => false).stdout.split("\t").first.strip
-  end
-end
-
 class Buffer < StringIO
   def initialize(tty = false)
     super()
@@ -169,6 +153,20 @@ module Cask::Utils
     end
   end
 
+  # our own version of Homebrew's abv, with better defenses
+  # against unusual filenames
+  def self.cabv(dir)
+    output = ''
+    count = Cask::SystemCommand.run!('/usr/bin/find',
+                                     :args => [dir, *%w[-type f -not -name .DS_Store -print0]],
+                                     :print_stderr => false).stdout.count("\000")
+    size = Cask::SystemCommand.run!('/usr/bin/du',
+                                    :args => ['-hs', '--', dir],
+                                    :print_stderr => false).stdout.split("\t").first.strip
+    output << "#{count} files, " if count > 1
+    output << size
+  end
+
   # paths that "look" descendant (textually) will still
   # return false unless both the given paths exist
   def self.file_is_descendant(file, dir)