Added GitSubmoduleCheck.cmake module

CMakeLists.txt

@@ -15,6 +15,18 @@ set(PROJECT_REPOSITORY https://github.com/sfztools/sfizz)
 
 # External configuration CMake scripts
 set(CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH};${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
+# Ensure presence of Git submodules (when not using the source tarball)
+if(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git")
+    include(GitSubmoduleCheck)
+    git_submodule_check(external/abseil-cpp)
+    git_submodule_check(external/filesystem)
+    git_submodule_check(external/simde)
+    git_submodule_check(external/st_audiofile/thirdparty/dr_libs)
+    git_submodule_check(external/st_audiofile/thirdparty/libaiff)
+    git_submodule_check(external/st_audiofile/thirdparty/wavpack)
+endif()
+
 include(BuildType)
 
 # Build Options

cmake/GitSubmoduleCheck.cmake

@@ -0,0 +1,13 @@
+find_package(Git REQUIRED)
+
+# https://gist.github.com/scivision/bb1d47a9529e153617414e91ff5390af
+
+function(git_submodule_check dir)
+    if(NOT EXISTS "${dir}/CMakeLists.txt")
+        execute_process(COMMAND ${GIT_EXECUTABLE} submodule update --init --recursive -- ${dir}
+            WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+            COMMAND_ERROR_IS_FATAL ANY)
+    endif()
+#   Add a Git submodule directory to CMake, assuming the Git submodule directory is a CMake project.
+#   add_subdirectory(${dir} EXCLUDE_FROM_ALL)
+endfunction()