How can I fetch a commit message in AWS CodePipeline/CodeBuild to implement a `[skip ci]` command?

I'm using an AWS CodePipeline with GitHub Connections as the source action to deploy a Python app to an AWS Elastic BeanStalk. I’d like to emulate GitHub Actions' [skip ci] feature by detecting a commit message prefix and exiting early if present, canceling the build stage.

I found this post, but the commented solution doesn't work with GitHub connections as the source of the action.

I added the following to my buildspec.yml:

version: 0.2

env:
  git-credential-helper: yes

phases:
  install:
    runtime-versions:
      python: 3.12
    commands:
      - COMMIT_MESSAGE=$(git log -1 --pretty=%B)
      - if [[ "$COMMIT_MESSAGE" == *"[skip ci]"* ]]; then echo "Skipping build"; exit 0; fi

But the build fails almost immediately with:

fatal: not a git repository (or any parent up to mount point /codebuild)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).

[Container] 2025/04/09 18:15:33.812706 Command did not exit successfully COMMIT_MESSAGE=$(git log -1 --pretty=%B) exit status 128
[Container] 2025/04/09 18:15:33.846916 Phase complete: INSTALL State: FAILED
[Container] 2025/04/09 18:15:33.846931 Phase context status code: COMMAND_EXECUTION_ERROR Message: Error while executing command: COMMIT_MESSAGE=$(git log -1 --pretty=%B). Reason: exit status 128

It looks like the CodeBuild environment directory isn’t recognized as a Git repository, so git command don't work.

Is there a built‑in way for CodePipeline/CodeBuild to expose the commit message as an environment variable or parameter? If direct access isn’t possible, what workaround would you recommend (e.g., using a Lambda pre‑build step, custom webhook, or other mechanism)?

Any example snippets of a working buildspec.yml or pipeline configuration would be greatly appreciated.

Thank you for your time!

I've figured out how to do it. Here were the steps for me, considering my CodePipeline consists of Source (CodeConnections) -> Build (CodeBuild) -> Deploy (Elastic Beanstalk):

1. Set the variable namespace in the source stage. I chose SourceVariables.
2. Create the COMMIT_MSG environment variable in the build stage as #{SourceVariables.CommitMessage} with the Plaintext type.
3. Create the PIPELINE_NAME environment variable in the build stage with the hardcoded value of your pipeline name and the Plaintext type.
4. Create the PIPELINE_EXECUTION_ID environment variable in the build stage as #{codepipeline.PipelineExecutionId} with the Plaintext type.
5. Grant the codepipeline:StopPipelineExecution permission to the CodeBuild service role on your CodePipeline resource.
6. Add some form of the below exerpt to your buildspec:

phases:
  build:
    commands:
      - |
        if [[ "$COMMIT_MSG" == *"[skip ci]"* ]]; then
          echo "Skipping EBS deploy"
          aws codepipeline stop-pipeline-execution \
            --pipeline-name "$PIPELINE_NAME" \
            --pipeline-execution-id "$PIPELINE_EXECUTION_ID" \
            --reason "Skip CI commit prefix"
          exit 0
        fi