[SOLVED] How can an AWS CodeBuild job see which files have changed?

How can an AWS CodeBuild job see which files have changed?

I'm trying to set up an AWS CodeBuild project to run tests to validate PRs and commits on a GitHub repository.

Because of the nature of the repo (a monorepo combining several ML models):

I need to restrict down to only run tests associated with files changed in the PR/commit to keep time+cost under control, but
The tests will typically require reference to other un-changed files in the repo: So can't just only pull changed files through to the build container.

How can a running CodeBuild build triggered by a GitHub PR (as per the docs here) 'see' which files are changed by the PR to selectively execute tests?

Solution

You can use git diff --name-only $CODEBUILD_RESOLVED_SOURCE_VERSION $CODEBUILD_WEBHOOK_PREV_COMMIT

Where $CODEBUILD_WEBHOOK_PREV_COMMIT is the commit id of the previous commit. And $CODEBUILD_RESOLVED_SOURCE_VERSION is the commit id of the actual one.

Inside a build phase you can check the change with:

- |
    if [ "$(git diff --name-only $CODEBUILD_RESOLVED_SOURCE_VERSION $CODEBUILD_WEBHOOK_PREV_COMMIT | grep -e <filde_path>)" != "" ]; then
      #your code;
    fi