brew style: assume files under Library are no-formulae

Library/Homebrew/style.rb

@@ -57,12 +57,24 @@ module Homebrew
         args << "--only" << cops_to_include.join(",")
       end
 
+      has_non_formula = Array(files).any? do |file|
+        File.expand_path(file).start_with? HOMEBREW_LIBRARY_PATH
+      end
+      config_file = if files.nil? || has_non_formula
+        if ARGV.include?("--rspec")
+          HOMEBREW_LIBRARY_PATH/".rubocop-rspec.yml"
+        else
+          HOMEBREW_LIBRARY_PATH/".rubocop.yml"
+        end
+      else
+        HOMEBREW_LIBRARY/".rubocop_audit.yml"
+      end
+
+      args << "--config" << config_file
+
       if files.nil?
-        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"
         args += files
       end
 

Library/Homebrew/test/cmd/style_spec.rb

@@ -31,4 +31,18 @@ describe "brew style" do
         .to include("Extra empty line detected at class body beginning.")
     end
   end
+
+  describe "Homebrew::check_style_and_print" do
+    let(:dir) { mktmpdir }
+
+    it "returns false for conforming file with only audit-level violations" do
+      # This file is known to use non-rocket hashes and other things that trigger audit,
+      # but not regular, cop violations
+      target_file = HOMEBREW_LIBRARY_PATH/"utils.rb"
+
+      rubocop_result = Homebrew::Style.check_style_and_print([target_file])
+
+      expect(rubocop_result).to eq false
+    end
+  end
 end