Tests/RunCMake/FetchContent/DownloadTwice.cmake - third_party/github.com/Kitware/CMake - Git at Google

 cmake_policy(SET CMP0169 OLD)

 include(FetchContent)

 FetchContent_Declare(
   t1
   DOWNLOAD_COMMAND ${CMAKE_COMMAND} -E echo "Download command executed"
 )

 FetchContent_Populate(t1)
 FetchContent_Populate(t1) # Triggers error
	cmake_policy(SET CMP0169 OLD)

	include(FetchContent)

	FetchContent_Declare(
	t1
	DOWNLOAD_COMMAND ${CMAKE_COMMAND} -E echo "Download command executed"
	)

	FetchContent_Populate(t1)
	FetchContent_Populate(t1) # Triggers error