Attempt to fix the submodule_regression test (#16)
A number of submodules are currently failing the submodule_regression test with "NO PRIMARY BRANCH TO TEST!" messages -- this is due to not having the proper origin/main branch to test against.
I think this can be fixed by doing a git fetch in the submodule after we run a git submodule sync, just to make sure the info for the current URL is up-to-date. This is still having a bit of an issue sometimes on the test server due to permissions issues, but we're mostly good and we can revisit things once we go public with the repos.