[ci] Adds github action for creating batch release (#10298)

fixes flutter/flutter#176425

To set up a batch release cron job for a package, one needs to make a copy of packages/.github/workflows/go_router_batch.yml, and change the name and cron schedule.

The cron job does the following:
1. trigger batch_release_pr.yaml with the input package

batch_release_pr:
1. check out repo
2. Run script/tool/lib/src/branch_for_batch_release_command.dart to create branches with all the changes
3. create pr request

## Pre-Review Checklist

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Author: chunhtai

.github/workflows/batch_release_pr.yml

@@ -0,0 +1,43 @@
+name: "Creates Batch Release for A Package"
+
+on:
+  repository_dispatch:
+    types: [batch_release_pr]
+
+jobs:
+  create_release_pr:
+    runs-on: ubuntu-latest
+    env:
+      BRANCH_NAME: ${{ github.event.client_payload.package }}-${{ github.run_id }}-${{ github.run_attempt }}
+    steps:
+      - name: checkout repository
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
+      - name: Set up tools
+        run: dart pub get
+        working-directory: ${{ github.workspace }}/script/tool
+      # This step is to create a branch for batch release
+      # A branch may not be created if there is nothing to release.
+      # In that case, the workflow will exit and complete successfully.
+      - name: create batch release PR
+        run: |
+          git config --global user.name ${{ secrets.USER_NAME }}
+          git config --global user.email ${{ secrets.USER_EMAIL }}
+          dart ./script/tool/lib/src/main.dart branch-for-batch-release --packages=${{ github.event.client_payload.package }} --branch=${{ env.BRANCH_NAME }} --remote=origin
+      - name: Check if branch was created
+        id: check-branch-exists
+        uses: GuillaumeFalourd/[email protected]
+        with:
+          branch: ${{ env.BRANCH_NAME }}
+
+      - name: Create Pull Request
+        if: steps.check-branch-exists.outputs.exists == 'true'
+        uses: peter-evans/create-pull-request@v7
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          commit-message: "[${{ github.event.client_payload.package }}] Batch release"
+          title: "[${{ github.event.client_payload.package }}] Batch release"
+          body: "This PR was created automatically to batch release the `${{ github.event.client_payload.package }}`."
+          branch: ${{ env.BRANCH_NAME }}
+          base: release
+
+

.github/workflows/go_router_batch.yml

@@ -0,0 +1,17 @@
+name: "Creates Batch Release for go_router"
+
+on:
+  schedule:
+    # Run every Monday at 8:00 AM
+    - cron: "0 8 * * 1"
+
+jobs:
+  dispatch_release_pr:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Repository Dispatch
+        uses: peter-evans/repository-dispatch@v4
+        with:
+          token: "${{ secrets.GITHUB_TOKEN }}"
+          event-type: batch_release_pr
+          client-payload: '{"package": "go_router"}'

packages/go_router/pending_changelogs/template.yaml

@@ -0,0 +1,6 @@
+# Use this file as template to draft a unreleased changelog file.
+# Make a copy of this file in the same directory, rename it, and fill in the details.
+changelog: |
+  - Can include a list of changes.
+  - with markdown supported.
+version: <major|minor|patch|skip>

packages/go_router/pending_changelogs/test_only_1.yaml

@@ -0,0 +1,6 @@
+# This file is for test purposes only.
+# TODO(chuntai): remove this file before publishing.
+changelog: |
+  - Adds 'batch' option to CI config for go_router package.
+  - Updates GitHub Actions workflow for batch releases of go_router.
+version: major

packages/go_router/pending_changelogs/test_only_2.yaml

@@ -0,0 +1,5 @@
+# This file is for test purposes only.
+# TODO(chuntai): remove this file before publishing.
+changelog: |
+  - Adds some other features
+version: minor