Scenario: submodule-in-linked-worktree

A submodule, checked out in the monorepo and in a linked worktree of it.

Monorepo, on main: vendor/a/ is a submodule of the upstream, checked out.
Linked worktree ../feature/, on feature: the same submodule, initialized and checked out there too.
Upstream: seed.

Converting the submodule on main removes its settings, submodule.<name>.*, from .git/config. All worktrees share that file, so the submodule in ../feature/ counts as uninitialized from then on. Git itself advises against several worktrees of a monorepo with submodules: "the support for submodules is incomplete", says the git worktree documentation.

Output

setup.bash builds this state:

$ build_scenario scenario_submodule_in_linked_worktree

Before, the other worktree has the submodule initialized:

$ git -C ../feature submodule status
 bde416459fbcc09c9b585f3b65a94cab3f68bfcd vendor/a (heads/main)

$ git splice clone --from-submodule vendor/a
===  vendor/a: fetching $UPSTREAM
ok   vendor/a: cloned bde4164 from the submodule
===  vendor/a: the submodule's repository stays in .*/monorepo/\.git/modules/vendor/a -- remove it once you don't need it (regex)

After, the submodule's settings are gone, for every worktree:

$ git config --get-regexp '^submodule\.' || echo "no submodule settings"
no submodule settings

$ git -C ../feature submodule status
-bde416459fbcc09c9b585f3b65a94cab3f68bfcd vendor/a

../feature/ still has the files, but git submodule update skips the submodule until git submodule update --init sets it up again:

$ ls ../feature/vendor/a
file.txt

$ git -C ../feature submodule update && git -C ../feature submodule status
-bde416459fbcc09c9b585f3b65a94cab3f68bfcd vendor/a

Merging main into feature fails like in every checkout that has the submodule's files, a colleague's clone too: from the merge's view they're untracked files in the way.

$ git -C ../feature merge -q main
error: The following untracked working tree files would be overwritten by merge:
	vendor/a/file.txt
Please move or remove them before you merge.
Aborting
[1]

git submodule deinit -f removes the checkout, also here, where the submodule's settings are gone already. Then the merge converts the submodule in feature too:

$ git -C ../feature submodule deinit -q -f vendor/a && git -C ../feature merge -q main && git -C ../feature status --short && ls -A ../feature/vendor/a
.splice
file.txt

Output​

Output