Interactive rebase with submodules

I've encountered a scenario where git rebase --interactive drops a commit which contains a modification to a submodule but no other changes.

This occurs when there is a conflict when applying the commit (for example if the submodule's history has been rewritten and you are rewriting the parent repository to match the new version of the submodule).

To clarify:

git rebase -i # Edit a commit, switching submodule to an unrelated commit git rebase --continue # Conflict in submodule, checkout the correct submodule commit git add path/to/submodule # Only change in index is updated submodule git rebase --continue # No commit is created for the submodule change

This appears to be because the git-rebase--interactive script inspects whether there is anything to commit when `rebase --continue` is invoked by running:

     git diff-index --cached --quiet --ignore-submodules HEAD --

Is there a reason for the `--ignore-submodules` in this command? Removing that option results in the expected behaviour.

I can understand not updating submodules while running the rebase, but I expected that having resolved a conflict and added my change to the index it would be applied by `git rebase --continue`, as indeed it is if there happen to be other (non-submodule) changes in the same commit.