Split out rspec-specific Rubocop config to fix warning

Library/Homebrew/.rubocop-rspec.yml

@@ -0,0 +1,6 @@
+inherit_from:
+  - .rubocop.yml
+
+RSpec/ExpectActual:
+  Exclude:
+    - 'test/missing_formula_spec.rb'

Library/Homebrew/.rubocop.yml

@@ -88,7 +88,3 @@ Style/HashSyntax:
 # so many of these in formulae but none in here
 Style/TrailingBodyOnMethodDefinition:
   Enabled: true
-
-Rspec/ExpectActual:
-  Exclude:
-    - 'test/missing_formula_spec.rb'

Library/Homebrew/cmd/style.rb

@@ -112,7 +112,8 @@ module Homebrew
     end
 
     if files.nil?
-      args << "--config" << HOMEBREW_LIBRARY_PATH/".rubocop.yml"
+      config_file = ARGV.include?("--rspec") ? ".rubocop-rspec.yml" : ".rubocop.yml"
+      args << "--config" << HOMEBREW_LIBRARY_PATH/config_file
       args << HOMEBREW_LIBRARY_PATH
     else
       args << "--config" << HOMEBREW_LIBRARY/".rubocop_audit.yml"