[BUG] interactive rebase loses instruction sheet when aborting to avoid overwriting files

[using v2.1.3]

When using "rebase -i" and the working dir contains untracked files that are present
in the new base, we correctly get a "would be overwritten by checkout" error, but then
the whole rebase interrupts the (long) listing of the incriminated files in the middle
of a line and terminates with:

Aborting
could not detach HEAD

And consequently we are not rebasing any more, and the precious instruction sheet has been
lost.