How do you version a specific file ?

There are times when I want to version a specific file and leave the previously versioned files intact.

But Elixir doesn't let me do that. Every time I run mix.version to update a file, It removes the previous versioned files in rev.manifest.json.

For example, I have these resources in my html page:

- app.js
- app.css
- vendor.js
- vendor.css

And I'm using versioning on the first 2 files so the output is something like:

- app-04e29eccbc.js
- app-43c3e19kkbs.css
- vendor.js
- vendor.css

Now let's say I've updated vendor.css and I want to use elixir versioning to bust the cache for this particular file. If I pass in mix.version('./public/css/vendor.css'), what happens is that the vendor.css does get versioned but Elixir would get rid of the other ones. And the output becomes:

- app.js
- app.css
- vendor.js
- vendor-08ghhk37vqk.css

How can I overcome this issue? Is there any solution?