`git reset` for delete + intent-to-add doesn't reset

[Anthony Sottile <asottile@xxxxxxxxx>]

```
git --version
rm -rf t
git init t
cd t
touch a
git add a
git commit -m "add a"
git rm a
touch a
git add --intent-to-add a
git status --short
git reset -- a
git status --short
```

(the git version below is compiled from
ecbdaf0899161c067986e9d9d564586d4b045d62)

```
$ bash -x t.sh
+ git --version
git version 2.20.GIT
+ rm -rf t
+ git init t
Initialized empty Git repository in /tmp/t/t/.git/
+ cd t
+ touch a
+ git add a
+ git commit -m 'add a'
[master (root-commit) 95a1815] add a
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 a
+ git rm a
rm 'a'
+ touch a
+ git add --intent-to-add a
+ git status --short
DA a
+ git reset -- a
Unstaged changes after reset:
A    a
+ git status --short
DA a
```

Even `git reset --intent-to-add -- a` or `git checkout -- a` don't
seem to clear the `intent-to-add` state

How do I reset the intent-to-add status in this case?

Anthony