Prepare for Homebrew Cask to be imported.

- ignore Cask's files in `readall` (for now, there's an intentional
  syntax error that will need fixed)
- run Cask's tests if they exist
- don't check Cask's files in coverage reports (for now)

Library/Homebrew/cmd/readall.rb

@@ -15,6 +15,7 @@ module Homebrew
       ]
       Dir.glob(scan_files).each do |rb|
         next if rb.include?("/vendor/")
+        next if rb.include?("/cask/")
         ruby_files << rb
       end
 

Library/Homebrew/dev-cmd/test-bot.rb

@@ -671,6 +671,11 @@ module Homebrew
         test "brew", "tests", "--generic", *tests_args
         test "brew", "tests", "--no-compat", *tests_args_no_compat
         test "brew", "readall", "--syntax"
+        if OS.mac? &&
+           (HOMEBREW_REPOSITORY/"Library/Homebrew/cask/cmd/brew-cask-tests.rb").exist?
+          test "brew", "cask-tests"
+        end
+
         # TODO: try to fix this on Linux at some stage.
         if OS.mac?
           # test update from origin/master to current commit.

Library/Homebrew/test/.simplecov

@@ -12,6 +12,7 @@ SimpleCov.start do
   # tests to be dropped. This causes random fluctuations in test coverage.
   merge_timeout 86400
 
+  add_filter "/Homebrew/cask/"
   add_filter "/Homebrew/compat/"
   add_filter "/Homebrew/test/"
   add_filter "/Homebrew/vendor/"