ref-in-want does not consider namespace

Hello,

I am experimenting with the ref-in-want feature using a custom client and plain `git-upload-pack` on the server end. To my suprise, it turned out that fetching from a namespaced repository requires the `want-ref` lines to specify the refs in namespaced form. That is:

Say I have the ref `refs/namespaces/foo/refs/heads/main`. I launch upload-pack with `--namespace=foo`. Running `ls-refs` with a namespace-relative

  `ref-prefix refs/heads/*`

will work as expected, but sendingr

  `want-ref refs/heads/main`

will result in

  `ERR unknown ref refs/heads/main`

Sending

  `want-ref refs/namespaces/foo/refs/heads/main`

works, and the corresponding `wanted-refs` section will contain the ref as given (ie. including the namespace path).

Since my understanding of git namespaces is that they should be transparent to the client, I find this surprising.

I dug up an early version of a patch introducing the feature, which did handle namespaces [0], but what eventually landed (authored by Brandon Williams) didn't.

Was this an oversight, or is there a specific reason for the behaviour?

Thanks, Kim

[0]: https://lore.kernel.org/git/d0d42b3bb4cf755f122591e191354c53848f197d.1485381677.git.jonathantanmy@google.com/