Add googletest upgrade guide

Author: scheibel

source/tests/README.md

@@ -0,0 +1,25 @@
+## Update googletest and googlemock
+
+After updating, the following changes needs to be applied manually:
+
+* https://github.com/cginternals/cmake-init/commit/6df2e5acd0111ca13f4a54f616a8e9e729f3fedc
+* https://github.com/cginternals/cmake-init/commit/da2b52c0b8b47989d779b8285c1a0294a71947ac
+* https://github.com/cginternals/cmake-init/commit/f505bef30fe3122d7bd3b8061fcf704fac452d7f
+* https://github.com/cginternals/cmake-init/commit/217786a6e8ab1c3a69ab899ec7fba06d5516452a
+
+### Explicit diff
+
+`googletest/googlemock/CMakeLists.txt`
+
+Add `set(BUILD_SHARED_LIBS OFF)` after the call to `option(BUILD_SHARED_LIBS ...)`
+Add `set(CMAKE_MACOSX_RPATH OFF)` before the calls to `cxx_library(...)`
+Add `set_target_properties(gmock_main PROPERTIES FOLDER "Tests")` after the calls to `cxx_library(...)`
+Add `set_target_properties(gmock      PROPERTIES FOLDER "Tests")` after the calls to `cxx_library(...)`
+
+`googletest/googletest/CMakeLists.txt`
+
+Add `set(BUILD_SHARED_LIBS OFF)` after the call to `option(BUILD_SHARED_LIBS ...)`
+Add `set(CMAKE_MACOSX_RPATH OFF)` before the calls to `cxx_library(...)`
+Add `set_target_properties(gtest_main PROPERTIES FOLDER "Tests")` after the calls to `cxx_library(...)`
+Add `set_target_properties(gtest      PROPERTIES FOLDER "Tests")` after the calls to `cxx_library(...)`
+Comment out the calls to `install`