Several "recovery" commands outright fail or do not fully recover
when directory-file conflicts are present. This includes:
* git read-tree --reset HEAD
* git am --skip
* git am --abort
* git merge --abort
* git reset --hard
Add testcases documenting these shortcomings.
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>