Get the latest sha for a git repo within a Concourse task

get-latest-sha.yml

---
platform: linux
image_resource:
  type: registry-image
  source:
    password: ((ce-dockerhub-token))
    repository: alpine/git
    username: ((ce-dockerhub-id))
inputs:
  - name: source-code
outputs:
  - name: sha
run:
  path: sh
  args:
    - -cxe
    - |
      git --git-dir=source-code/.git rev-parse --short HEAD > sha/sha
      cat sha/sha