namespace HEAD issue

hello, everybody.
here is my bare repo
test_namespace.git$ tree

cat ./refs/namespaces/A/HEAD
ref: refs/heads/master
irb>require "rugged"
irb>repo=Rugged::Repository.new(".")
irb>repo.namespace="A"
irb>repo.head #=>result is ok

and git-upload-pack failed. here is error msg

~/Code/test/ git clone  git@newgit.com:zouqilin/test_namespace.git
Cloning into 'test_namespace'...
remote: Counting objects: 6, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 6 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (6/6), done.
Checking connectivity... done.
Note: checking out '0f2055ccfb11e0490de20f7c8673b7676981b8bc'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

if i change do as follow.

$> echo "ref: refs/namespaces/A/heads/master"

irb>repo.head# failed
Rugged::ReferenceError: Reference 'refs/namespaces/A/refs/heads/master' not found
    from (irb):5:in `head'
    from (irb):5
    from /usr/local/bin/irb:11:in `<main>'

but git-upload-pack is ok in this case.
so what should i do?

Reproduce the namespace HEAD behavior with the bare repository, Rugged::Repository#namespace, and repo.head, then compare the two refs/namespaces/A/HEAD contents shown. Check how git-upload-pack resolves each reference and determine the expected behavior for Rugged and Git compatibility.