cmake: update submodules automatically during the build

CMakeLists.txt

@@ -363,7 +363,7 @@ ENDIF()
 
 SET (MYSQLD_STATIC_PLUGIN_LIBS "" CACHE INTERNAL "")
 
-# mariadb_connector_c fetches submodules which is useful for plugins
+INCLUDE(submodules)
 INCLUDE(mariadb_connector_c) # this does ADD_SUBDIRECTORY(libmariadb)
 
 # Add storage engines and plugins.

cmake/mariadb_connector_c.cmake

-IF(NOT EXISTS ${CMAKE_SOURCE_DIR}/libmariadb/CMakeLists.txt AND GIT_EXECUTABLE)
-  EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule init
-                  WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
-  EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update
-                  WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}")
-ENDIF()
-IF(NOT EXISTS ${CMAKE_SOURCE_DIR}/libmariadb/CMakeLists.txt)
-  MESSAGE(FATAL_ERROR "No MariaDB Connector/C! Run
-    git submodule init
-    git submodule update
-Then restart the build.
-")
-ENDIF()
-
 SET(OPT CONC_)
 
 IF (CMAKE_BUILD_TYPE STREQUAL "Debug")

cmake/submodules.cmake

+# update submodules automatically
+IF(GIT_EXECUTABLE AND EXISTS "${CMAKE_SOURCE_DIR}/.git")
+  EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" config --get cmake.update-submodules
+                  WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+                  OUTPUT_VARIABLE cmake_update_submodules)
+  IF(cmake_update_submodules MATCHES no)
+    SET(update_result 0)
+  ELSEIF (cmake_update_submodules MATCHES force)
+    MESSAGE("-- Updating submodules (forced)")
+    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init --force
+                    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+                    RESULT_VARIABLE update_result)
+  ELSEIF (cmake_update_submodules MATCHES yes)
+    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init
+                    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+                    RESULT_VARIABLE update_result)
+  ELSE()
+    MESSAGE("-- Updating submodules")
+    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init
+                    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+                    RESULT_VARIABLE update_result)
+  ENDIF()
+ENDIF()
+
+IF(update_result OR NOT EXISTS ${CMAKE_SOURCE_DIR}/libmariadb/CMakeLists.txt)
+  MESSAGE(FATAL_ERROR "No MariaDB Connector/C! Run
+    git submodule update --init
+Then restart the build.
+")
+ENDIF()