github-team-approver

GitHub application to manage approvals to release software.

Installing

Registering as a GitHub App

The first step towards installing github-team-approver is to generate a secret meant to allow validation of incoming payloads. It is recommended that this secret is generated using 1Password (or any other method that generates a cryptographically secure secret). Then, you should proceed to registering github-team-approver as a GitHub application using this link, and according to the following instructions:

• GitHub App Name: Choose a meaningful value.
• Homepage URL: Choose a meaningful value.
• Webhook URL: Choose https://<host>/ (where <host> is the host where the application is exposed).
• Webhook Secret: The secret created above.
• SSL Verification: Depending on your setup, you may need to choose "Disable (not recommended)".
• Permissions: Choose the following sets of permissions:
  • Repository permissions:
    • Contents: Read only
    • Pull requests: Read & write
    • Commit statuses: Read & write
  • Organisation permissions:
    • Members: Read only
• Subscribe to events: Tick the following checkboxes:
  • Pull request
  • Pull request review
• Where can this GitHub App be installed? Choose "Any account".

Upon successful registration, you'll be taken to the GitHub application's administration page. Take note of the value of the "App ID" field, as it will be needed later on. Then, scroll down to the bottom of the page and click "Generate a private key". This will generate and download the GitHub application's private key, which will be used to authenticate the application with GitHub. Take note of the path to where the private key is downloaded. Finally, click on the "Install App" tab, choose the target GitHub organization and click "Install" (possibly choosing only a subset of the GitHub organization's repositories).

Upon successful installation, you'll be taken to a page having a URL of following form:

https://github.com/organizations/<org>/settings/installations/<installation-id>

Take note of the value of <installation-id>, as it will be needed later on.

Running

github-team-approver is meant to run as a standalone application on top of Kubernetes. Hence, a Kubernetes cluster is required to run github-team-approver. For local development and testing, this may correspond to a Docker Desktop or Minikube cluster. For production, a managed offering of Kubernetes such as GKE or EKS is strongly recommended.

Once you've got a running Kubernetes cluster, run the following command to create the required secret containing the GitHub application's private key, webhook secret token and optionally a 256 bit key if you want to use slack alerts:

$ make secret \
    GITHUB_APP_PRIVATE_KEY_PATH=<path-to-private-key> \
    GITHUB_APP_WEBHOOK_SECRET_TOKEN_PATH=<path-to-webhook-secret-token> 

Then, run the following command to build and deploy github-team-approver in development mode:

$ make skaffold.dev \
    GITHUB_APP_ID=<app-id> \
    GITHUB_APP_INSTALLATION_ID=<installation-id>

NOTE: Depending on your setup, you may need to specify a custom Docker image using the DOCKER_IMG and DOCKER_TAG variables in the command above.

NOTE: If you are using AWS ECR as the container registry, you may need to run the following command:

docker login <registry> --username AWS --password $(aws ecr get-login-password)

Configuring

When called in result of a pull request event, github-team-approver reads its configuration from the .github/GITHUB_TEAM_APPROVER.yaml file in the default branch of the repository from which the event originated. It then analyses the body of the source pull request, as well as its reviews, and determines whether to approve the pull request based on that data. The aforementioned configuration file must obey the following format:

pull_request_approval_rules:
- target_branches:
  - "<name>"
  - "<name>"
  rules:
  - regex: "<regex>"
    regex_labels: "<regex>"
    directories:
      - "<direcotry>"
    approving_team_handles:
    - "<id-or-name-or-slug>"
    - "<id-or-name-or-slug>"
    - "<id-or-name-or-slug>"
    approval_mode: "<approval-mode>"
    labels:
    - "<label>"
    - "<label>"
    force_approval: false # or true!
  alerts:
   - regex: '- \[x\] Emergency\.'
     slack_message: "emergency change merged <PR_URL>"

Each item under pull_request_approval_rules represents how approval for PRs made to specific target branches should work, according to the following table:

Field	Description
regex	Regular expression to match the body of the pull request against. If matched, approval from each listed team will be required.
regex_label	Regular expression to match label(s) of the pull request against. If matched, approval from each listed team will be required.
directories	Optional list of relative or absolute paths to directories that should be checked for changes. If not provided, all directories are checked.
approving_team_handles	The list of approving teams, in the form of IDs, names or slugs.
approval_mode	One of require_any or require_all.
labels	The set of labels to apply to the pull request. Labels are prefixed with the github-team-approver/ prefix.
force_approval	Whether to automatically approve PRs matching the regular expression without waiting for review.
ignore_contributors_approval	Whether to ignore approvals of people who pushed a commit to the PR or are a co-author of at least one of the commits.

Each item under alert represents a slack alert that will fire if regex is matched:

Field	Description
regex	Regular expression to match the body of the pull request against. If matched, slack alert will be fired
slack_message	Slack webhook you wish to post, should be a json object that matches slack.WebhookMessage. Set text field for plain message or you can use the blocks field to build a fancy message. The slack_message field will be put through go templating with the PR event, so you can template out anything from that payload. For an example see template, see examples/templates/merged.template

A live example of a configuration file can be seen here.

Slack integration

In order to send a slack alert you need to register a slack app and setup a webhook to a channel. Upon doing this slack will generate a secret url, do not share this url as it will enable anyone to post to your slack channel.

Expose your generated webhook in SLACK_WEBHOOK_SECRET variable.

Remarks

• Each team listed under approving_team_handles should have "Read" access (at least) to the repository.
• If the target_branches field is omitted or left empty, the specified rules are applied to all PRs regardless of the target branch.
• PRs made against branches for which no rules are defined are automatically marked as approved.
• PRs made against branches for which rules are defined MUST match at least one rule to be approved.
• At the moment detecting co-authors supports only noreply email addresses from GitHub.