Features:
- send slack notifications about successful and failed builds;
 - link to build details in slack message;
 - no need in additional step in cloudbuild.yaml;
 - report success and failure statuses;
 - show trigger information in slack message;
 - customize slack message using substitution in cloudbuild.yaml.
 
Prerequisites:
- Google Cloud Platform project with enabled Cloud Functions API;
 - gcloud command-line util authorized to deploy cloud functions;
 - Slack webhook url.
 
Deployment:
SLACK_WEBHOOK_URL=https://hooks.slack.com/services/YOUR_TOKENS ./deploy.shThis script will deploy cloud function gcbSubscribeSlack triggered by cloud-build PubSub topic.
Message content can be (optionally) defined by _SLACK_MESSAGE_TEMPLATE substitution in cloudbuild.yaml. Value should be a valid ejs template:
steps:
# ... build steps ...
substitutions:
  _SLACK_MESSAGE_TEMPLATE: '<%= emoji %> *https://<%= build.substitutions._OVERLAY %>.example.com* frontend build & deploy `<%= build.id %>` <%= build.status %>'emoji corresponds to a build status, build is object containing build information, it's structure is defined here.
The default message template is <%= emoji %> `<%= build.id %>` <%= build.status %>

