stash tests: stash can lose data in a file removed from the index

stash tests: stash can lose data in a file removed from the index

If a file is removed from the index and then modified in the working
tree then stash will discard the working tree file with no way to
recover the changes.

This can might be done in one of a number of ways.

git rm file
vi file              # edit a new version
git stash

or with git mv

git mv file newfile
vi file              # make a new file with the old name
git stash

Signed-off-by: Charles Bailey <charles@hashpling.org>