docs: clarify the interaction of transfer.hideRefs and namespaces

Expand the section about namespaces in the documentation of
`transfer.hideRefs` to point out the subtle differences between
`upload-pack` and `receive-pack`.

9bedd82 (upload-pack.c: treat want-ref relative to namespace,
2021-07-30) taught `upload-pack` to reject `want-ref`s for hidden refs,
which is now documented.

Signed-off-by: Kim Altintop <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: kim

Documentation/config/transfer.txt

@@ -52,13 +52,16 @@ If you have multiple hideRefs values, later entries override earlier ones
 (and entries in more-specific config files override less-specific ones).
 +
 If a namespace is in use, the namespace prefix is stripped from each
-reference before it is matched against `transfer.hiderefs` patterns.
-For example, if `refs/heads/master` is specified in `transfer.hideRefs` and
-the current namespace is `foo`, then `refs/namespaces/foo/refs/heads/master`
-is omitted from the advertisements but `refs/heads/master` and
-`refs/namespaces/bar/refs/heads/master` are still advertised as so-called
-"have" lines. In order to match refs before stripping, add a `^` in front of
-the ref name. If you combine `!` and `^`, `!` must be specified first.
+reference before it is matched against `transfer.hiderefs` patterns. For
+example, if `refs/heads/master` is specified in `transfer.hideRefs` and the
+current namespace is `foo`, then `refs/namespaces/foo/refs/heads/master` is
+omitted from the advertisements. If `uploadpack.allowRefInWant` is set,
+`upload-pack` will treat `want-ref refs/heads/master` in a protocol v2
+`fetch` command as if `refs/heads/master` was unknown. Note, however, that
+`receive-pack` will still advertise the object id `refs/heads/master` is
+pointing to, but will conceil the name of the ref. In order to match refs
+before stripping, add a `^` in front of the ref name. If you combine `!` and
+`^`, `!` must be specified first.
 +
 Even if you hide refs, a client may still be able to steal the target
 objects via the techniques described in the "SECURITY" section of the