Update advanced.md

master branch changed to main branch in links

docs/advanced.md

@@ -1142,8 +1142,8 @@ GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(FooTest);
 
 You can see [sample7_unittest.cc] and [sample8_unittest.cc] for more examples.
 
-[sample7_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample7_unittest.cc "Parameterized Test example"
-[sample8_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample8_unittest.cc "Parameterized Test example with multiple parameters"
+[sample7_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample7_unittest.cc "Parameterized Test example"
+[sample8_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample8_unittest.cc "Parameterized Test example with multiple parameters"
 
 ### Creating Value-Parameterized Abstract Tests
 
@@ -1294,7 +1294,7 @@ TYPED_TEST(FooTest, HasPropertyA) { ... }
 
 You can see [sample6_unittest.cc] for a complete example.
 
-[sample6_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample6_unittest.cc "Typed Test example"
+[sample6_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample6_unittest.cc "Typed Test example"
 
 ## Type-Parameterized Tests
 
@@ -1733,7 +1733,7 @@ You can do so by adding one line:
 Now, sit back and enjoy a completely different output from your tests. For more
 details, see [sample9_unittest.cc].
 
-[sample9_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample9_unittest.cc "Event listener example"
+[sample9_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample9_unittest.cc "Event listener example"
 
 You may append more than one listener to the list. When an `On*Start()` or
 `OnTestPartResult()` event is fired, the listeners will receive it in the order
@@ -1760,7 +1760,7 @@ by the former.
 
 See [sample10_unittest.cc] for an example of a failure-raising listener.
 
-[sample10_unittest.cc]: https://github.com/google/googletest/blob/master/googletest/samples/sample10_unittest.cc "Failure-raising listener example"
+[sample10_unittest.cc]: https://github.com/google/googletest/blob/main/googletest/samples/sample10_unittest.cc "Failure-raising listener example"
 
 ## Running Test Programs: Advanced Options