CMP0097ΒΆ
New in version 3.16.
ExternalProject_Add() with GIT_SUBMODULES "" initializes no
submodules. The policy also applies to FetchContent_Declare(),
which uses the same download and update features as
ExternalProject_Add().
The commands provide a GIT_SUBMODULES option which controls what submodules
to initialize and update. Starting with CMake 3.16, explicitly setting
GIT_SUBMODULES to an empty string means no submodules will be initialized
or updated.
This policy provides compatibility for projects that have not been updated to expect the new behavior.
The OLD behavior for this policy is for GIT_SUBMODULES when set to
an empty string to initialize and update all git submodules.
The NEW behavior for this policy is for GIT_SUBMODULES when set to
an empty string to initialize and update no git submodules.
This policy was introduced in CMake version 3.16. Use the
cmake_policy() command to set it to OLD or NEW explicitly.
Unlike most policies, CMake version 3.27.9 does not warn
when this policy is not set and simply uses OLD behavior.