[BUG] git rebase is confuse if conflict resolution doesn't produce diff

To reproduce:
- Rebase a branch "foo" on a branch "bar" in a way that there is a
conflict that you have to manually resolve.
- Run git diff and see the conflict
- Edit the conflicted file and remove all the conflicting bits (that
could be a valid resolution of the conflict)
- Now git diff produces an empty diff
- git add $CONFLICTED_FILE  as you have resolve the conflict
- git rebase --continue

You get the following error: No changes - did you forget to use 'git add'?

git status is empty as the conflict was resolved.

A simple workaround is to add a dummy blank line in the conflicted file so the diff is not empty.

	G.