Implement Github notification bot.

Using https://github.com/GoogleCloudPlatform/cloud-build-notifiers as
a base, created a Github bot that will add the details of the Google
Cloud build to each pull request.

Closes #259

build/ci/github-bot/Dockerfile

@@ -0,0 +1,22 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+FROM golang AS build-env
+COPY . /go-src
+WORKDIR /go-src
+RUN go build -o /go-app .
+
+FROM gcr.io/distroless/base
+COPY --from=build-env /go-app /
+ENTRYPOINT ["/go-app", "--alsologtostderr", "--v=0"]

build/ci/github-bot/Makefile

@@ -0,0 +1,34 @@
+# Copyright 2021 Google LLC All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+STORAGE := gs://quilkin-ci-config
+
+current_dir := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
+
+all: build deploy
+
+# build: creates the project Cloud Build custom build step and hosts it on gcr.io
+build:
+	gcloud builds submit . --config=cloudbuild.yaml $(ARGS)
+
+# deploy pushes a new version to Cloud Run
+deploy:
+	-gsutil mb $(STORAGE)
+	gsutil cp $(current_dir)/github.yaml $(STORAGE)
+	gcloud run deploy github-bot \
+		--image="us-docker.pkg.dev/quilkin/ci/github-bot" \
+		--platform managed \
+		--no-allow-unauthenticated \
+		--region=us-west3 \
+		--update-env-vars="CONFIG_PATH=$(STORAGE)/github.yaml"

build/ci/github-bot/README.md

@@ -0,0 +1,30 @@
+# Github Notification Bot
+
+This is the bot that created comments on GitHub pull requests whenever a 
+[Google Cloud Build](https://cloud.google.com/build) build passes or fails.
+
+## Setup
+
+### Image
+
+Run `make build` to submit the cloud build to create the image that will be hosted on 
+[Cloud Run](https://cloud.google.com/run). 
+
+### Secrets
+
+It is expected that there will be a secret named `gh-token` with a 
+[Github auth token](https://docs.github.com/en/github/authenticating-to-github/creating-a-personal-access-token) stored
+in it, and the ${PROJECT_NUMBER}-compute@developer.gserviceaccount.com service account has the
+role `roles/secretmanager.secretAccessor` for the `gh-token` secret.
+
+### Deployment
+
+Run `make deploy` to copy the config to the appropriate bucket, and deploy the notifier image to Cloud Run.
+
+### Connect to Cloud Build
+
+Follow https://cloud.google.com/build/docs/subscribe-build-notifications to create the
+[Google Cloud PubSub topics](https://cloud.google.com/pubsub) for Google Cloud Build. 
+
+Follow https://cloud.google.com/run/docs/triggering/pubsub-push to setup the Notifier service to be triggered from
+PubSub with the `cloud-builds` pubsub topic.

build/ci/github-bot/cloudbuild.yaml

@@ -0,0 +1,26 @@
+# Copyright 2021 Google LLC All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+steps:
+  - name: gcr.io/cloud-builders/docker
+    args:
+      - build
+      - --tag=${_REGISTRY}/github-bot:latest
+      - '.'
+images:
+  - ${_REGISTRY}/github-bot
+options:
+  dynamic_substitutions: true
+substitutions:
+  _REGISTRY: "us-docker.pkg.dev/${PROJECT_ID}/ci"

build/ci/github-bot/github.yaml

@@ -0,0 +1,25 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+apiVersion: cloud-build-notifiers/v1
+kind: GithubNotifier
+metadata:
+  name: github-notifier
+spec:
+  notification:
+    filter: build.status == Build.Status.SUCCESS
+    delivery:
+  secrets:
+    - name: gh-token
+      value: projects/quilkin/secrets/gh-token/versions/latest

build/ci/github-bot/go.mod

@@ -0,0 +1,26 @@
+// Copyright 2021 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+module github-bot
+
+go 1.16
+
+require (
+	github.com/GoogleCloudPlatform/cloud-build-notifiers/lib/notifiers v0.0.0-20210219212036-163c92a64b27
+	github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b
+	github.com/google/go-github/v35 v35.2.0
+	golang.org/x/oauth2 v0.0.0-20210201163806-010130855d6c
+	golang.org/x/tools v0.1.1 // indirect
+	google.golang.org/genproto v0.0.0-20210513213006-bf773b8c8384
+)