Merge branch 'sb/submodule-abort-update-upon-config-failure'

"git submodule update" learned to abort early when core.worktree
for the submodule is not set correctly to prevent spreading damage.

* sb/submodule-abort-update-upon-config-failure:
  git-submodule: abort if core.worktree could not be set correctly

git-submodule.sh

@@ -548,7 +548,7 @@ cmd_update()
 	do
 		die_if_unmatched "$quickabort" "$sha1"
 
-		git submodule--helper ensure-core-worktree "$sm_path"
+		git submodule--helper ensure-core-worktree "$sm_path" || exit 1
 
 		update_module=$(git submodule--helper update-module-mode $just_cloned "$sm_path" $update)