Regression[2.14.3->2.15]: Interactive rebase fails if submodule is modified

[Orgad Shaneh <orgads@gmail.com>]

I can't reproduce this with a minimal example, but it happens in my project.

What I tried to do for reproducing is:
rm -rf super sub
mkdir sub; cd sub; git init
git commit --allow-empty -m 'Initial commit'
mkdir ../super; cd ../super
git init
git submodule add ../sub
touch foo; git add foo sub
git commit -m 'Initial commit'
touch a; git add a; git commit -m 'a'
touch b; git add b; git commit -m 'b'
cd sub; git commit --allow-empty -m 'New commit'; cd ..
git rebase -i HEAD^^

Then drop a.

In my project I get:
error: cannot rebase: You have unstaged changes.

This works fine with 2.14.3.

- Orgad