REVERT remove upgrade line
TRY PARTIAL: another submodule at same location
Revert "TRY PARTIAL: another submodule at same location"

This reverts commit faa1275d3828771cb73b8938752c0cdeb09d2cb8.
TRY TEST: some test
Revert "TRY TEST: some test"

This reverts commit 75c76459a88de80e68e994820d78f2d5f7b230d6.
t7410-submodule-checkout-to.sh: more cases for "update --init"

Verify that the resulted submodules are always independent on their behavior.
Do not check the internal data of repositories. So, any valid implementation
should pass the tests.
Revert modules back to common

The new approach is always keep submodules in main worktree, and
make them linked in linked worktrees of super-repository.
submodule: refactor to allow positional parameters
submodule refactor: use rev-path --git-path instead of manually constructed paths
submodule: make update --init create linked submodule worktree when called in linked main worktree