implement Path::join()

test/src/test_Path.cc

@@ -21,3 +21,9 @@ TEST(PathTest, convert_backslashes_to_forward_slashes)
     Path p("C:\\foo\\bar.txt");
     EXPECT_EQ("C:/foo/bar.txt", p.to_s());
 }
+
+TEST(PathTest, joins_two_paths_together)
+{
+    EXPECT_EQ("C:/foo/../baz", Path("C:\\foo").join("../baz").to_s());
+    EXPECT_EQ("/xyz/f.txt", Path("/xyz/").join("f.txt").to_s());
+}