empty metadata updates result in a vague error and update infinite loop

[iomarcovalente]

Describe the bug

For the update action if the metadata file is not changed we get a vague error:
failed to update the lock: bootstrap-terragrunt-builds-lock! (err: exit status 1) retrying...
and the task is stuck in an infinite update loop, can't even abort the pipeline.

I found that if I do change the content of the file every time it will not error out.
So I can only assume that exit status 1 is probably git erroring out during one of the git commands, likely git commit

I suggest that the code is changed to cater for that scenario.

// Check if there are any changes
status, err := glh.git("status", "--porcelain")
if err != nil {
    return "", err
}

// If there are changes, commit them
if status != "" {
    commitMessage := glh.messagePrefix() + fmt.Sprintf("%s: %s", operation, lockName)
    _, err = glh.git("commit", lockPath, "-m", commitMessage)
    if err != nil {
        return "", err
    }
}

as above, I would very naively just run commit if there are changes but there might be other parts involved that I am not aware of.

Reproduction steps

Run the following pipeline (change the lock repo accordingly), twice, to test:

meta:
  # Secrets that are populated by the global credentials manager or var_sources
  secrets:
    github_private_key: &github_private_key ((github-private-key))

resources:
  - name: terragrunt-builds-locks
    type: pool
    source:
      uri: git@github.com:<<your-repo-here>>.git
      branch: main
      pool: bootstrap-terragrunt-builds
      private_key: *github_private_key

jobs:
  - name: claim-lock
    plan:
      - in_parallel:
          fail_fast: true
          steps:
            - get: terragrunt-builds-locks
              trigger: false
              params:
                depth: 10

      - task: create-lock-info
        output_mapping:
          output: bootstrap-terragrunt-builds-lock-info
        config:
          image_resource:
            type: docker-image
            source: {repository: busybox}
          platform: linux
          outputs:
            - name: output
          run:
            path: sh
            args:
            - -cex
            - |
              WORKDIR="${PWD}"
              # create a lock-info file that contains the lock name and
              # the lock metadata for the pool resource to consume
              echo "bootstrap-terragrunt-builds-lock" > ${WORKDIR}/output/name
              echo "TEST" > ${WORKDIR}/output/metadata

      - put: terragrunt-builds-locks-update
        resource: terragrunt-builds-locks
        params:
          update: bootstrap-terragrunt-builds-lock-info

      - put: terragrunt-builds-locks-claim
        resource: terragrunt-builds-locks
        params:
          claim: bootstrap-terragrunt-builds-lock

      - put: terragrunt-builds-locks-release
        resource: terragrunt-builds-locks
        params:
          release: terragrunt-builds-locks-claim

it will succeed the first time and fail the second time.

Expected behavior

to not fail if the metadata file content is not changing

Additional context

No response