Fix heuristic for Unix Assembly with .ms extension (#3550)

lib/linguist/heuristics.rb

@@ -298,7 +298,7 @@ module Linguist
       if /^[.'][a-z][a-z](\s|$)/i.match(data)
         Language["Groff"]
       elsif /(?<!\S)\.(include|globa?l)\s/.match(data) || /(?<!\/\*)(\A|\n)\s*\.[A-Za-z]/.match(data.gsub(/"([^\\"]|\\.)*"|'([^\\']|\\.)*'|\\\s*(?:--.*)?\n/, ""))
-        Language["GAS"]
+        Language["Unix Assembly"]
       else
         Language["MAXScript"]
       end

test/test_heuristics.rb

@@ -178,6 +178,13 @@ class TestHeuristcs < Minitest::Test
     })
   end
 
+  def test_ms_by_heuristics
+    assert_heuristics({
+      "Unix Assembly" => all_fixtures("Unix Assembly", "*.ms"),
+      "MAXScript" => all_fixtures("MAXScript", "*.ms")
+    })
+  end
+
   # Candidate languages = ["C++", "Objective-C"]
   def test_obj_c_by_heuristics
     # Only calling out '.h' filenames as these are the ones causing issues