GlobList: added a clear test for pattern priority

[gribozavr]

Summary

The last glob that matches the string decides whether that string is
included or excluded.

[ilya-biryukov]

LGTM

clang-tools-extra/unittests/clang-tidy/GlobListTest.cpp

TEST(GlobList, Everything) {
 
   EXPECT_TRUE(Filter.contains(""));
   EXPECT_TRUE(Filter.contains("aaaa"));
   EXPECT_TRUE(Filter.contains("-*"));
   EXPECT_TRUE(Filter.contains("-"));
   EXPECT_TRUE(Filter.contains("*"));
 }
 
-TEST(GlobList, Simple) {
+TEST(GlobList, OneSimplePattern) {
   GlobList Filter("aaa");
 
   EXPECT_TRUE(Filter.contains("aaa"));
   EXPECT_FALSE(Filter.contains(""));
   EXPECT_FALSE(Filter.contains("aa"));
   EXPECT_FALSE(Filter.contains("aaaa"));
   EXPECT_FALSE(Filter.contains("bbb"));
 }
 
+TEST(GlobList, TwoSimplePatterns) {
+  GlobList Filter("aaa,bbb");
+
+  EXPECT_TRUE(Filter.contains("aaa"));
+  EXPECT_TRUE(Filter.contains("bbb"));
+  EXPECT_FALSE(Filter.contains(""));
+  EXPECT_FALSE(Filter.contains("aa"));
+  EXPECT_FALSE(Filter.contains("aaaa"));
+  EXPECT_FALSE(Filter.contains("bbbb"));
+}
+
+TEST(GlobList, PatternPriority) {
+  // The last glob that matches the string decides whether that string is
+  // included or excluded.
+  {
+    GlobList Filter("a*,-aaa");
+
+    EXPECT_FALSE(Filter.contains(""));
+    EXPECT_TRUE(Filter.contains("a"));
+    EXPECT_TRUE(Filter.contains("aa"));
+    EXPECT_FALSE(Filter.contains("aaa"));
+    EXPECT_TRUE(Filter.contains("aaaa"));
+  }
+  {
+    GlobList Filter("-aaa,a*");
+
+    EXPECT_FALSE(Filter.contains(""));
+    EXPECT_TRUE(Filter.contains("a"));
+    EXPECT_TRUE(Filter.contains("aa"));
+    EXPECT_TRUE(Filter.contains("aaa"));
+    EXPECT_TRUE(Filter.contains("aaaa"));
+  }
+}
+
 TEST(GlobList, WhitespacesAtBegin) {
   GlobList Filter("-*,   a.b.*");
 
   EXPECT_TRUE(Filter.contains("a.b.c"));
   EXPECT_FALSE(Filter.contains("b.c"));
 }
 
 TEST(GlobList, Complex) {