[RFC] URL rewrite in .gitmodules

Hi,

I have a closed source Git repo which references an Open Source Git repo as Submodule. The Open Source Git repo references yet another Open Source repo as submodule. In order to avoid failing builds due to external services I mirrored the Open Source repos in my company network. That works great with the first level of Submodules. Unfortunately it does not work with the second level because the first level still references the "outside of company" repos. I know I can rewrite Git URLs with the git config "url.<base>.insteadOf" option. However, git configs are client specific. I would prefer a solution that works without setup on any client. I also know that I could update the .gitmodules file in the Open Source repo on the first level. I also would prefer not to do this as I want to use the
  very same hashes as defined by the "upstream" Open Source repos.

Is there yet another way in Git to change URLs of Submodules in the way I want it?

If not, what do you think about a patch that adds a "url" section similar to the one in git config to a .gitmodules file?

Example:
----------
[submodule "git"]
	path = git
        url=git://github.com/larsxschneider/git.git

[url "mycompany.com"]
        insteadOf = outside.com
----------

Thanks, Lars