Submodules or similar for exercise/exam management

Hi all

[Jens, I was hoping you'd have some insight, but of course everyone is welcome to join in. I honestly never thought I'd get into the submodule business so shortly after gittogether...]

Out of $DAYJOB issues with tracking exercises and exams, I had a little brainstorming session with a fellow assistant yesterday. It seems none of this has been done before? Is anyone else interested (mainly in getting the requirements right so that the next poor soul won't have to roll their own)?

The scenario is that we have a bunch of exercise questions stored in one or several files, each living in a directory. Then, we assemble those into exercise sheets (super-repos) spanning a group of questions (submodules). We would like to track this in such a way that changes to the questions propagate to other sheets (possibly in other lectures) that use them.

Training everyone in full git usage is probably not an option, so any solution would have to have some frontend that can be explained easily.

The requirements we came up with are roughly:

1) commit across all sub-repos at the same time (atomicity nice but
   optional)

  1b) tag across all sub-repos

2) do recursive clone/update of one super-repo easily

3) never need to be aware of repo boundaries or manipulate sub-repo

4) sanely cope with branches etc. in case the user wants them

A sample workflow might be:

  foo clone git@example.com/some/super/repo
  # time passes
  cd repo
  foo update
  # work
  foo status
  foo diff
  foo commit -m 'one message fits all'
  # possibly, but this could also be commit --no-push instead
  foo push

Merges are expected to be rare but would happen every so often.

It seems repo can do (2) and (4) but violates (3) [requires use of git-commit and others in the sub-repo]. git-subtree can do (1) and (2) but probably violates (3) [need to rebase changes to sub-repo branch] and (4). Submodules can do (2) and (4) but violate (3) and currently have no support for (1). I think svn externals could do (1)-(3) but violate (4) and probably (1b).

Has this been done before? Or do we need to hack up a new wrapper around submodules?