push from one remote to another

[Olaf Hering <olaf@aepfle.de>]

What is the correct syntax/setup to push from one remote to another?
I did something like this, to feed a github repo:

 # rm -rf $$
 # mkdir $$
 # cd $$
 # git --init
 # git remote add --tags t git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
 # git remote add --tags o git@github.com:user/repo.git
 # git fetch --all

This syntax does not work for me:
 # git push t master o master
 # git push --tags t master o master

Is there a way to kind of mirror without doing a checkout, to save
diskspace?

Olaf