Action fails when there are no SAM changes

Start with template.yml and the “SAM Validate, Build, Test, Deploy” workflow, focusing on the failing “SAM deploy” step. Reproduce the failure by rerunning a completed workflow without SAM template changes, then verify that the job succeeds and reports no deployment changes when there is nothing to deploy.

Describe the bug
When a change is pushed to main which doesn't update the SAM template, the deployment job will fail.

To Reproduce
Steps to reproduce the behavior:
The previous workflow must have completed successfully, and the repo hasn't been updated.

1. Go to Actions
2. Click on workflow "SAM Validate, Build, Test, Deploy"
3. Choose "Re-run jobs"

This job will fail

Expected behavior
The running job should succeed

Screenshots
Step "SAM deploy" fails with the following error:

(note that I ran this from my own fork, so the stack name is different to what you will expect)

A possible fix: Change the last command in template.yml to the following:

      sam deploy --template-file .aws-sam/build/template.yaml \
        --stack-name ${{ steps.vars.outputs.environment }} \
        --s3-bucket ${{ steps.vars.outputs.environment }} \
        --parameter-overrides \
          'ParameterKey=Name,ParameterValue=example \
          ParameterKey=Version,ParameterValue=${{ steps.vars.outputs.version }}' \
        --capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM \
        || echo "Nothing to deploy, no changes"