Added disambiguation rule and tests for '*.s', '*.S'

lib/rouge/guessers/disambiguation.rb

@@ -146,6 +146,13 @@ def match?(filename)
         next Prolog if matches?(/\A\w+(\(\w+\,\s*\w+\))*\./)
         next OpenEdge
       end
+
+      disambiguate '*.s', '*.S' do
+        next GnuAsm if matches?(/\s*\.(global|extern|type|text)/)
+        next GnuAsm if matches?(/%(r|e)(ax|bx|cx|dx|si|di|bp|sp)/)
+
+        ArmAsm
+      end
     end
   end
 end

spec/lexers/armasm_spec.rb

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+describe Rouge::Lexers::ArmAsm do
+  let(:subject) { Rouge::Lexers::ArmAsm.new }
+
+  describe 'guessing' do
+    include Support::Guessing
+
+    it 'guesses by filename and source hint' do
+      assert_guess :filename => 'foo.s', :source => 'Func MOVW    r0, #RetVal'
+    end
+  end
+end

spec/lexers/gnuasm_spec.rb

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+describe Rouge::Lexers::GnuAsm do
+  let(:subject) { Rouge::Lexers::GnuAsm.new }
+
+  describe 'guessing' do
+    include Support::Guessing
+
+    it 'guesses by filename and source hint' do
+      assert_guess :filename => 'foo.s', :source => 'main: movq %rax, %rbx'
+    end
+  end
+end