MDEV-28032 "git submodule update --depth 1" may fail with old Git

submodules.cmake: don't use "--depth 1" with old Git

Old Git may not work with "--depth 1" when the referenced commit hash
is far from HEAD.

Newer Git improves the situation. For example:
https://github.com/git/git/commit/fb43e31f2b43076e7a30c9cd00d0241cb8cf97eb

It's safe to not use "--depth 1" with old Git.

Closes #2049

cmake/submodules.cmake

@@ -17,21 +17,30 @@ IF(GIT_EXECUTABLE AND EXISTS "${CMAKE_SOURCE_DIR}/.git")
     ${GIT_EXECUTABLE} config cmake.update-submodules yes")
   ELSEIF(git_config_get_result EQUAL 128)
     SET(update_result 0)
-  ELSEIF (cmake_update_submodules MATCHES force)
+  ELSE()
+    SET(UPDATE_SUBMODULES_COMMAND
+        "${GIT_EXECUTABLE}" submodule update --init --recursive)
+    # Old Git may not work with "--depth 1".
+    # See also: https://github.com/git/git/commit/fb43e31f2b43076e7a30c9cd00d0241cb8cf97eb
+    IF(NOT GIT_VERSION_STRING VERSION_LESS "2.8.0")
+      SET(UPDATE_SUBMODULES_COMMAND ${UPDATE_SUBMODULES_COMMAND} --depth 1)
+    ENDIF()
+    IF(cmake_update_submodules MATCHES force)
       MESSAGE(STATUS "Updating submodules (forced)")
-    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init --force --depth=1
+      EXECUTE_PROCESS(COMMAND ${UPDATE_SUBMODULES_COMMAND} --force
                       WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
                       RESULT_VARIABLE update_result)
-  ELSEIF (cmake_update_submodules MATCHES yes)
-    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init --depth=1
+    ELSEIF(cmake_update_submodules MATCHES yes)
+      EXECUTE_PROCESS(COMMAND ${UPDATE_SUBMODULES_COMMAND}
                       WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
                       RESULT_VARIABLE update_result)
     ELSE()
       MESSAGE(STATUS "Updating submodules")
-    EXECUTE_PROCESS(COMMAND "${GIT_EXECUTABLE}" submodule update --init --depth=1
+      EXECUTE_PROCESS(COMMAND ${UPDATE_SUBMODULES_COMMAND}
                       WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
                       RESULT_VARIABLE update_result)
     ENDIF()
+  ENDIF()
 ENDIF()
 
 IF(update_result OR NOT EXISTS ${CMAKE_SOURCE_DIR}/libmariadb/CMakeLists.txt)