.github/workflows: add go-licenses GitHub Action

.github/licenses.tmpl

@@ -0,0 +1,19 @@
+{{/*
+
+This template is used to generate the license notices published at
+https://github.com/tailscale/tailscale/blob/main/licenses/android.md.
+Publishing is managed by the go-licenses GitHub Action.  Non-Go dependencies
+should be manually updated at the bottom of this file as needed.
+
+*/}}# Tailscale for Android dependencies
+
+The following open source dependencies are used to build the [Tailscale Android
+Client][].  See also the dependencies in the [Tailscale CLI][].
+
+[Tailscale Android Client]: https://github.com/tailscale/tailscale-android
+
+## Go Packages
+
+{{ range . }}
+ - [{{.Name}}](https://pkg.go.dev/{{.Name}}) ([{{.LicenseName}}]({{.LicenseURL}}))
+{{- end }}

.github/workflows/go-licenses.yml

@@ -0,0 +1,66 @@
+name: go-licenses
+
+on:
+  # run action when a change lands in the main branch which updates go.mod or
+  # our license template file. Also allow manual triggering.
+  push:
+    branches:
+      - main
+    paths:
+      - go.mod
+      - .github/licenses.tmpl
+      - .github/workflows/go-licenses.yml
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  licenses:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+
+      - name: Check out OSS code
+        uses: actions/checkout@v3
+        with:
+          repository: tailscale/tailscale
+          path: oss
+
+      - name: Set up Go
+        uses: actions/setup-go@v3
+        with:
+          go-version-file: go.mod
+
+      - name: Install go-licenses
+        run: |
+          go install github.com/google/go-licenses@v1.2.2-0.20220825154955-5eedde1c6584
+
+      - name: Run go-licenses
+        run: |
+          go-licenses report ./cmd/tailscale --template .github/licenses.tmpl | tee oss/licenses/android.md
+
+      - name: Get access token
+        uses: tibdex/github-app-token@f717b5ecd4534d3c4df4ce9b5c1c2214f0f7cd06 # v1.6.0
+        id: generate-token
+        with:
+          app_id: ${{ secrets.LICENSING_APP_ID }}
+          installation_id: ${{ secrets.LICENSING_APP_INSTALLATION_ID }}
+          private_key: ${{ secrets.LICENSING_APP_PRIVATE_KEY }}
+
+      - name: Send pull request
+        uses: peter-evans/create-pull-request@18f90432bedd2afd6a825469ffd38aa24712a91d #v4.1.1
+        with:
+          token: ${{ steps.generate-token.outputs.token }}
+          path: oss
+          author: License Updater <noreply@tailscale.com>
+          branch: licenses/android
+          branch-suffix: short-commit-hash
+          commit-message: "licenses: update android licenses"
+          title: "licenses: update android licenses"
+          body: Triggered by ${{ github.repository }}@${{ github.sha }}
+          delete-branch: true
+          team-reviewers: opensource-license-reviewers