Resource not updated when only submodule has changes (because of cache)

[ThibaultDelaune-pro]

Describe the bug

I have a repo with multiple git submodules within. When changes appear in any of that submodule, even if I have submodule_remote: true, the corresponding resource is not updated because of cache existance.

Reproduction steps

1. create a Git repo with any content in it --> child-repo
2. create another Git repo with child-repo as a Git submodule --> parent-repo
3. create a pipeline with a resource on parent-repo
4. create a job wich make a get on parent-repo (with submodule_remote param)
5. launch a first time the job
6. make a change on child-repo
7. launch the job again
8. observe that the resource hasn't change ("INFO: found existing resource cache")
   ...

Expected behavior

At 8th step, I expect that the resource fetch the parent-repo in order to have the latest changes in any of its childs repos.

Additional context

parent-repo

|_ child-repo/
|_ somefile

child-repo

|_ README

pipeline.yaml

resources:
- name: my-repo
  type: git
  source:
    uri: ssh://git@git-scm.***:2222/parent-repo.git
    private_key: ******
    branch: master

jobs:
- name: test
  plan:
  - get: parent-repo
    params:
      submodule_remote: true
  - task: show-readme-content
    config:
      platform: linux
      image_resource:
        type: registry-image
        source:
          repository: busybox
      inputs:
      - name: git-repo
      run:
        path: /bin/sh
        args:
        - -ec
        - |
          cat git-repo/child-repo/README

If I modify the README just before the 2nd launch (6th step), I don't see the changes in the console!

it can also be noted that if I run fly crc -r my-pipeline/parent-repo, it does not work either.

Concourse version : v7.9.1