How to get the short sha for the github workflow?

I am creating a workflow in GitHub which creates and uses a docker image. Therefore I have started my workflow file with a global environment variable for this docker image which is visible for all the jobs in my workflow:

name: continuous integration
on:
  push:
    branches:
      - '**'

env:
  IMAGE: docker.pkg.github.com/${{ github.repository }}/jactor-persistence:${{ github.sha }}

I want to replace ${{ github.sha }} with the short sha of the head commit, the same as the result of the following command git rev-parse --short HEAD

Is this possible?

      - name: Set outputs
        id: vars
        run: echo "sha_short=$(git rev-parse --short HEAD)" >> $GITHUB_OUTPUT
      - name: Check outputs
        run: echo ${{ steps.vars.outputs.sha_short }}