Bug: git-stash fails for new file not staged for commit

> > What did you do before the bug happened?
>
> I tried to stash a new file that I added with `git add --intent-to-add`:
>
> ```
> $ touch foo
> $ git add --intent-to-add foo
> $ git stash
> ```
>
>
> > What did you expect to happen?
>
> The file should have been stashed.
>
>
> > What happened instead?
>
> The stash failed with the following error message:
>
> ```
> error: Entry 'foo' not uptodate. Cannot merge.
> Cannot save the current worktree state
> ```
>
>
> > What's different between what you expected and what actually happened?
>
> Instead of stashing the file, the stash fails with an error message.
>
>
> > Anything else you want to add:
>
> Background: https://github.com/okonet/lint-staged/issues/990
>
>
> [System Info]
> git version:
> git version 2.32.0

> cpu: x86_64
> no commit associated with this build
> sizeof-long: 8
> sizeof-size_t: 8
> shell-path: /bin/sh
> uname: Linux 5.4.72-microsoft-standard-WSL2 #1 SMP Wed Oct 28 23:40:43 
> UTC 2020 x86_64
> compiler info: gnuc: 9.3
> libc info: glibc: 2.31
> $SHELL (typically, interactive shell): /usr/bin/zsh
>
>
> [Enabled Hooks]
> applypatch-msg
> pre-applypatch
> post-applypatch
> pre-commit
> prepare-commit-msg
> commit-msg
> post-commit
> pre-rebase
> post-checkout
> post-merge
> pre-push
> pre-receive
> update
> post-receive
> post-update
> push-to-checkout
> pre-auto-gc
> post-rewrite
> sendemail-validate
>
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