Checkout file without changing index?

Hi,

what is the standard/recommended way for updating a file to given version?

I was familiar with "git checkout revision -- file".

But it updates both working tree and index. I had some changes in index (staged) and "git checkout HEAD -- file" silently overwritten it. Well, probably my mistake, it's documented.

After searching a bit I found "git show revision:file > file". But
it's problematic:
1. works only for 1 file. "git show revision -- file" does something else
2. requires full path, so you need to specify "git show
revision:relative/to/top/dir/file"

If there's no other easy way, maybe we could add "--no-index" to checkout: "git checkout --no-index revision -- file" (or similar - maybe use options from git-reset).

My use case: I had some changes prepared in index and wanted to compare the prepared version with some older version. The file was a zip file plus we use LFS so there was no other way than to "checkout" the file, unpack it and diff it.