Chetter monitors pull request events sent from Github and adds some quality of life improvements intended to assist code review.

Chetter References

A conscientious author might explicitly publish any changes they push to a pull request branch that is still under review. Likewise, a diligent reviewer might create local branch/tag pointing to the tip of the branch they reviewed so that it could be compared against later pull request updates. However, while we all wish each other the best, this is tedious work and easy to forget. Chetter takes care of all that by creating references in refs/heads/pr/<pull request>/.

Each version of a pull request, defined as push to a branch with an open pull request, is tracked by refs/heads/pr/<pull request>/v<version number>. Additionally, refs/heads/pr/<pull request>/head tracks the most recent version.

Similarly, a new reference is created each time a reviewer completes their review (submits a review with either Approval or Request changes). Each review is tracked as refs/heads/pr/<pull request>/<reviewer>-v<review number>, and refs/heads/pr/<pull request>/<reviewer>-head points to the most recent review.

Finally, all of the references mentioned in the two prior paragraphs also have an associated reference ending in -base which represents the base of the pull request at the time the versioned reference was made.

When a pull request is closed or merged, Chetter will delete all associated references.

Using Chetter References

What changed since you last reviewed pull request 10:

git diff origin/pr/10/<username>-head..origin/pr/10/head

Commits and changes between v1 and v2 of pull request 10 with the same base, origin/master:

git range-diff origin/master origin/pr/10/v1 origin/pr/10/v2

Commits and changes since you last reviewed after the pull request branch was rebased on new changes to origin/master and force pushed:

git range-diff \
        origin/pr/10/<username>-base..origin/pr/10/<username>-head \
        origin/pr/10/head-base..origin/pr/10/head

Pruning Chetter References

You may wish to enable automatic pruning so that local references are deleted when the pull request is closed.

git config --add remote.origin.prune true

Running Chetter

• Register a GitHub App

  • Select the Contents (read/write) and Pull Request (read-only) Repository Permissions
  • Enable the Pull Request and Pull Request Review event subscriptions
  • Set the Webhook URL to point to where chetter-app will be running
  • Note the application id
  • Generate a private key

• Create a chetter-app.toml configuration

  app_id = <application_id>
  private_key = """
  -----BEGIN RSA PRIVATE KEY-----
  ABCDE...
  -----END RSA PRIVATE KEY-----
  """
  

• Build the chetter-app container image

  make -C docker VERSION=latest chetter-app
  

• Create a container

  • Expose port 3333/tcp
  • Add the directory containing chetter-app.toml as a volume mounted at /config

  podman run --rm \
      --name chetter-app
      --publish 0.0.0.0:3333:3333/tcp \
      --volume /dir/containing/config:/config \
      chetter-app:latest