message: fixes dummy-hook's .git directory for multiple work trees
diff: -if(EXISTS "${Ginkgo_SOURCE_DIR}/.git")
  +find_package(Git QUIET)
  +if(GIT_FOUND)
  + execute_process(COMMAND ${GIT_EXECUTABLE} rev-parse --git-path hooks
  + WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
  + OUTPUT_VARIABLE Ginkgo_GIT_HOOKS_DIR
  + OUTPUT_STRIP_TRAILING_WHITESPACE)
  + get_filename_component(Ginkgo_GIT_HOOKS_DIR ${Ginkgo_GIT_HOOKS_DIR} REALPATH BASE_DIR ${CMAKE_SOURCE_DIR})
  +
  + if(EXISTS "${Ginkgo_GIT_HOOKS_DIR}")
  set(ADD_HOOK FALSE)
  - set(HOOK_LOCATION "${Ginkgo_SOURCE_DIR}/.git/hooks/pre-commit")
  + set(HOOK_LOCATION "${Ginkgo_GIT_HOOKS_DIR}/pre-commit")
  if(NOT EXISTS "${HOOK_LOCATION}")
  set(ADD_HOOK TRUE)
  else()
  @@ -16,3 +24,4 @@ if(EXISTS "${Ginkgo_SOURCE_DIR}/.git")
  configure_file(dummy_hook "${HOOK_LOCATION}" COPYONLY)
  endif()
  endif()
  +endif()
  