Error fetching submodule from submodule

Hi I think I may have found an error in the way git handles a submodule's submodule. Read further for the example (extracted from a real project).

* I have a main repository which has some submodules defined.
* One of the submodules is a common submodule which is also included
in one of the other submodules
* When running `git fetch --recurse-submodules` I get an error.

The error is "Could not access submodule 'common_submodule'"

``` $ git --version git version 2.21.0 ```

I created the following script to show (using Git-extras `git create` to simplify):

``` #!/usr/bin/env bash

if [ "$FORCE" = 'true' ]; then
  rm -rf submodule_experiment
fi

if [ -e submodule_experiment ]; then
  echo FATAL: folder submodule_experiment must not exist. Remove with FORCE=true
  exit 9
fi

mkdir submodule_experiment pushd submodule_experiment

git setup common_submodule pushd common_submodule echo 'common file' > common.txt git add common.txt git commit -m 'a file in the common submodule'

popd

git setup other_submodule pushd other_submodule git submodule add ../common_submodule git commit -m 'added submodule to other_submodule'

popd

git setup main_repos pushd main_repos git submodule add ../common_submodule git commit -m 'added submodule to main_repos'

git submodule add ../other_submodule git commit -m 'added other_submodule to main_repos'

# This line fails with error code 1 "Could not access submodule 'common_submodule'" git fetch --recurse-submodules

```

Question: Is this a bug in Git or am I declaring the common submodule in an incorrect way?