filter coverage result with vendored libraries and test code

Merged: https://github.com/ruby/ruby/pull/7185

tool/test-coverage.rb

@@ -4,6 +4,12 @@ Coverage.start(lines: true, branches: true, methods: true)
 
 TEST_COVERAGE_DATA_FILE = "test-coverage.dat"
 
+FILTER_PATHS = %w[
+  tool/lib
+  lib/bundler/vendor
+  test
+]
+
 def merge_coverage_data(res1, res2)
   res1.each do |path, cov1|
     cov2 = res2[path]
@@ -77,7 +83,7 @@ def invoke_simplecov_formatter
 
   res.each do |path, cov|
     next unless path.start_with?(base_dir) || path.start_with?(cur_dir)
-    next if path.start_with?(File.join(base_dir, "test"))
+    next if FILTER_PATHS.any? {|dir| path.start_with?(File.join(base_dir, dir))}
     simplecov_result[path] = cov
   end