Local cache for git objects

I'd like to speed up fetching objects from remote repositiories when creating
multiple clones on one or more machines in LAN.

I know it can be done by hand: git-fetch once and git-clone from local copy.
I think about adding new capability to upload-pack which would allow making
relay and object store. Client would supply url where "want"-ed objects should
be available.

Next I'd add config option for git-fetch with url of this cache.
fetch-pack would get refs from remote and request objects from cache.

I'm not sure if this hasn't been done.
Would such feature be included in git?