rebase --abort Unespected behavior

[Blaise Garant <blaise@garantcoutu.com>]

Hello,

I don't know if this is a bug but it was unexpected for us. I
accidentally added untracked files through a `git add .` while doing
an interactive rebase and aborting the rebase deleted those files. Is
this to be expected?

To reproduce:
mkdir test_folder
cd test_folder
git init
touch first
git add .
git commit -m 'First'
echo 1 >> first
git add .
git commit -m 'Second'
echo 2 >> first
git add .
touch second
git commit -m 'Third'
git rebase -i HEAD~2 #set second to be edited
git add .
git status        #second should have staged
git rebase --abort
ls        #second has been deleted

Not sure this is an expected behavior.
Thanks
Blaise Garant