Invalid url for get reference endpoint?

While this code works fine for most use cases:

https://github.com/KnpLabs/php-github-api/blob/de2f27846139e7b4b92dcad9ff77660d0dc5dfad/lib/Github/Api/GitData/References.php#L83

It looks like that `GET /refs/{ref}` is an undocumented endpoint and it returns an array of references when an exact reference is not found, but other similar references are found in the repo.

> Current GitHub docs tells to use `GET /ref/{ref}` URL: https://docs.github.com/en/rest/reference/git#get-a-reference

My story: I have the following references in the repo:

- accepted-1-1
- accepted-1-1-1

When I try to get `accepted-1` reference using `references()->show(..)` I get the following response, but I expect zero results:

If I change `GET /refs/{ref}` to `GET /ref/{ref}` in `References.php` it starts throwing a 404 not found exception as expected.

Start in lib/Github/Api/GitData/References.php at the referenced line and compare the requested path with GitHub's current get-a-reference documentation. Reproduce the lookup for a partial reference and verify that an exact missing reference no longer returns similarly named references; update the relevant behavior and add or adjust coverage where the repository's existing tests cover this endpoint.

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