[RFC] submodule+shallow clone feature request

My use case is deploying from a git repository, which would be even more graceful with the following features:

1. When 'git clone' has both --recursive and --depth, then submodules
are also checked out shallow (for speed/bandwidth).

2. Some way to specify an override on .gitmodules sources.  This is
because our .gitmodules includes public, read-only sources (github),
rather than our local repos we would prefer to deploy from (for the
purpose of reliability).

The other use-case for feature #2 is the read-only vs. writable repository sources. Developers that are also working on the submodules should be able to clone from separate repository sources. Though this could be (and perhaps is) satisfied with a pushurl= in .gitmodules, I'd like to keep the push url non-public, and that still would leave us unable to deploy from different urls.

For #2 maybe something like this:

$ git clone --recursive --depth 1 --modules foo.modules\

where foo.modules contains:
<begin>
[submodule "bar"]
	path = bar
	url = git@example.com/bar.git
[submodule "bar/baz"]
	path = bar/baz
	url = git@example.com/baz.git
<end>

Notice how the .gitmodules needs to be able to specify recursive sources as well. Presumably `git submodule init` would take --modules argument as well (and maybe git submodule update, too).

I'm not well-versed in the git source code yet, but poking around suggests that this is doable. Would a patch be well received (or does someone want to do it for me :-)

cheers, sky