To reproduce:

• make sure JGit is available as Git tool in your setup
• create a single branch pipeline from https://github.com/zbynek/submodule-grandparent , branch "main"
• add "advanced submodule behaviors" and either left all checkboxes blank or check only recursive checkout

Expected:

• command line git is used and build works

Actual

• JGit is used and build fails

Known workarounds: check some of the other checkboxes or fill in some fields (use parent credentials, max number of threads, ...)

Notes: the code handles these options one by one source, it may be better to simply disable JGit when the submodule block is present.