use cases for git namespaces

Hi,

It seems to me that whatever namespaces can do, can functionally be done using just a subdirectory of branches. The only real differences I can see are (a) a client sees less branch clutter, and (b) a fetch/clone pulls down less if the big stuff is in another namespace.

I would like to understand what other uses/reasons were thought of.

I looked for discussion on the ml archives. I found the patch series but could not easily find much *discussion* of the feature and its design. I found one post [1] that indicated that "part of the rationale..." (being what I described above), but I would like to understand the *rest* of the rationale.

Pointers to gmane are also fine, or brief descriptions of uses [being] made of this.

[1]: http://article.gmane.org/gmane.comp.version-control.git/175832/match=namespace

Thanks