Use a nicer template for messages

deployment/live/cloudbuild/README.md

@@ -1,4 +1,4 @@
-## Cloudbuild Triggers and Steps
+# Cloudbuild Triggers and Steps
 
 This directory contains a terragrunt file that can be deployed using `terragrunt apply` to define the necessary triggers and steps in GCB.
 These steps will:
@@ -13,7 +13,7 @@ Error: Error creating Trigger: googleapi: Error 400: Repository mapping does not
 
 This is a manual one-time step that needs to be followed to integrate GCB and the GitHub project.
 
-### Slack notifications
+## Slack Notifications
 
 Each cloudbuild environment sets up a Slack integration. This requires:
  1. A webhook to have been created in a Slack app (https://api.slack.com/apps/A06KYD43DPE/incoming-webhooks)
@@ -28,3 +28,65 @@ terragrunt import module.cloud-build-slack-notifier.google_pubsub_topic.cloud_bu
 ```
 
 This imports the resource into this configuration, and running `terragrunt apply` again after this should work.
+
+### Slack Templating
+
+Here's an example pub-sub message for ease of writing templates ([docs](https://pkg.go.dev/cloud.google.com/go/cloudbuild/apiv1/v2/cloudbuildpb#Build)):
+
+```
+{
+  "id": "0d97c63e-a349-4bf7-80d0-8f6e21786d87",
+  "status": "SUCCESS",
+  "source": {
+    "gitSource": {
+      "url": "https://github.com/transparency-dev/distributor.git",
+      "revision": "a017b5e59a1cf9fdbed5999e1a9aced5404de4cd"
+    }
+  },
+  "createTime": "2024-02-21T16:56:35.560619Z",
+  "steps": [{
+    "name": "gcr.io/cloud-builders/docker",
+    "args": ["build", "-t", "us-central1-docker.pkg.dev/checkpoint-distributor/distributor-docker-dev/distributor:latest", "-f", "./cmd/Dockerfile", "."]
+  }, {
+    "name": "gcr.io/cloud-builders/docker",
+    "args": ["push", "us-central1-docker.pkg.dev/checkpoint-distributor/distributor-docker-dev/distributor:latest"]
+  }, {
+    "name": "gcr.io/google.com/cloudsdktool/cloud-sdk",
+    "args": ["run", "deploy", "distributor-service-dev", "--image", "us-central1-docker.pkg.dev/checkpoint-distributor/distributor-docker-dev/distributor:latest", "--region", "us-central1"],
+    "entrypoint": "gcloud"
+  }],
+  "timeout": "600s",
+  "projectId": "checkpoint-distributor",
+  "sourceProvenance": {
+    "resolvedGitSource": {
+      "url": "https://github.com/transparency-dev/distributor.git",
+      "revision": "a017b5e59a1cf9fdbed5999e1a9aced5404de4cd"
+    }
+  },
+  "buildTriggerId": "33f60a9c-3d79-4941-bfb1-fccbdd9cf38c",
+  "options": {
+    "substitutionOption": "ALLOW_LOOSE",
+    "logging": "CLOUD_LOGGING_ONLY",
+    "dynamicSubstitutions": true,
+    "pool": {
+    }
+  },
+  "logUrl": "https://console.cloud.google.com/cloud-build/builds;region\u003dus-central1/0d97c63e-a349-4bf7-80d0-8f6e21786d87?project\u003d39300730911",
+  "substitutions": {
+    "TRIGGER_NAME": "build-distributor-docker-dev",
+    "COMMIT_SHA": "a017b5e59a1cf9fdbed5999e1a9aced5404de4cd",
+    "TRIGGER_BUILD_CONFIG_PATH": "",
+    "REPO_FULL_NAME": "transparency-dev/distributor",
+    "SHORT_SHA": "a017b5e",
+    "BRANCH_NAME": "main",
+    "REF_NAME": "main",
+    "REVISION_ID": "a017b5e59a1cf9fdbed5999e1a9aced5404de4cd",
+    "REPO_NAME": "distributor"
+  },
+  "tags": ["trigger-33f60a9c-3d79-4941-bfb1-fccbdd9cf38c"],
+  "queueTtl": "3600s",
+  "serviceAccount": "projects/checkpoint-distributor/serviceAccounts/cloudbuild-dev-sa@checkpoint-distributor.iam.gserviceaccount.com",
+  "name": "projects/39300730911/locations/us-central1/builds/0d97c63e-a349-4bf7-80d0-8f6e21786d87"
+}
+```
+

deployment/live/cloudbuild/dev/slack.json

@@ -1,14 +1,27 @@
 [
     {
-      "type": "section",
+      "type": "header",
       "text": {
-        "type": "mrkdwn",
-        "text": "Cloud Build {{.Build.ProjectId}} {{.Build.Id}} {{.Build.Status}}"
+        "type": "plain_text",
+        "text": "CloudBuild {{.Build.Status}}: {{.Build.Substitutions.REPO_NAME}} {{.Build.Substitutions.TRIGGER_NAME}}"
       }
     },
     {
       "type": "divider"
     },
+    {
+      "type": "section",
+      "fields": [
+        {
+          "type": "mrkdwn",
+          "text": "*Branch*: {{.Build.Substitutions.BRANCH_NAME}}"
+        },
+        {
+          "type": "mrkdwn",
+          "text": "*Commit*: {{.Build.Substitutions.SHORT_SHA}}"
+        }
+      ]
+    },
     {
       "type": "section",
       "text": {