git subtree push-all and pull-all

Hello,

I see over the last year (on the web and in this mailing list) there
was some activity to extend subtree with a .gittrees file and
push-all/pull-all commands.

Perhaps I missed it, but looking through the latest git code on the
github mirror I can't find any reference to the .gittrees file or
these commands.

Does anyone know the status of this feature? Was it decided that this
was a bad idea and the feature has been rejected? Or is this a feature
still "cooking"...which will likely make it into git mainline at some
point?

I ask because I would like to use something like this to be able to
keep a combined repository and separate project repositories in sync.
Of course, if it was decided that this feature is fundamentally a bad
idea then I will do something different.

Any pointers would be a big help.

thanks in advance,
Gareth Collins