The manual page says:

Git supports dividing the refs of a single repository into multiple namespaces, each of which has its own branches, tags, and HEAD.

Here, the mention of HEAD implies that requiring all namespaced to start with

refs/namespaces/*/refs

is too strict, as there are legal namespaced refs such as

refs/namespaces/*/HEAD

which are not captured. Relax the corresponding condition, change documentation and add a test to avoid regression.

REVIEW: update the example

In the commit message it said that we should be allowing refs/namespaces/xyz/HEAD, but in this example it used refs/HEAD.

REVIEW: match for refs or HEAD

Instead of allowing any component, we limit to either refs or HEAD.

Maybe we can be more relaxed here, but my thinking is that since we were strict before and want to allow for HEAD – as per the docs – then we just relax that and only that check.

Only allow HEAD as suggested by Fintan.