Mirroring for offline use - best practices?

Hi all,

I'm pretty sure this is a FAQ, but articles I found on the Internet were either mere "recipes" (i.e. tell you how, but don't explain why), or bogged down in so many details that I was never sure how to proceed from there.

Basic situation:

There's a master repository (Github or corporate or whatever), and I want to set up a local mirror so that I can create clones without having to access the original upstream. I'd like to set the mirror up so that creating a clone from it will automatically set up things to "just work": I.e. branches will track the mirror, not upstream, possibly other settings that I'm not aware of.

I gather that local clones are fast because hardlinked - is that correct? Is that correct on Windows? (I can't easily avoid Windows.)

Ramification 1:

I'm not sure how best to prepare patches for push-to-upstream. Is there value in collecting them locally into a push-to-upstream repo, or is it better to just push from each local clone individually?

Ramification 2:

Some of the repos I work with use submodules. Sometimes they use submodules that I'm not aware of. Or a submodule was used historically, and git bisect breaks/misbehaves because it can't get the submodule in offline mode. Is there a way to get these, without writing a script that recurses through all versions of .gitmodules? I'm seeing the --recurse-submodules option for git fetch, so this might (or might not) be the Right Thing.

Any thoughts welcome, thanks!

Regards, Jo