fix(submodules): make git submodule update always recursive (#30361)

Co-authored-by: Rhys Arkins <[email protected]>

Author: Josef-Reichardt

docs/usage/configuration-options.md

@@ -443,6 +443,7 @@ For `sbt` note that Renovate will update the version string only for packages th
 ## cloneSubmodules
 
 Enabling this option will mean that any detected Git submodules will be cloned at time of repository clone.
+Submodules are always cloned recursively.
 
 Important: private submodules aren't supported by Renovate, unless the underlying `ssh` layer already has the correct permissions.
 

lib/util/git/index.ts

@@ -354,7 +354,9 @@ export async function cloneSubmodules(shouldClone: boolean): Promise<void> {
   for (const submodule of submodules) {
     try {
       logger.debug(`Cloning git submodule at ${submodule}`);
-      await gitRetry(() => git.submoduleUpdate(['--init', submodule]));
+      await gitRetry(() =>
+        git.submoduleUpdate(['--init', '--recursive', submodule]),
+      );
     } catch (err) {
       logger.warn(
         { err },