CI: For every release PR created, also push a changelog PR to main (#90698)

For every release PR created, also push a changelog PR to main

.github/workflows/changelog.yml

@@ -1,5 +1,22 @@
 name: Generate changelog
 on:
+  workflow_call:
+    inputs:
+      version:
+        required: true
+        description: 'Target release version (semver, git tag, branch or commit)'
+      target:
+        required: true
+        type: string
+        description: 'The base branch that these changes are being merged into'
+      dry_run:
+        required: false
+        default: false
+        type: bool
+      latest:
+        required: false
+        default: false
+        type: bool
   workflow_dispatch:
     inputs:
       version:
@@ -84,8 +101,9 @@ jobs:
           fi
 
           git diff CHANGELOG.md
+          git add CHANGELOG.md
       - name: "Commit changelog changes"
-        run: git commit --allow-empty -m "Update changelog placeholder" CHANGELOG.md
+        run: git commit --allow-empty -m "Update changelog" CHANGELOG.md
       - name: "git push"
         if: ${{ inputs.dry_run }} != true
         run: git push

.github/workflows/release-comms.yml

@@ -58,18 +58,13 @@ jobs:
         echo dry run: ${{ needs.setup.outputs.dry_run }}
   create_github_release:
     # a github release requires a git tag
+    # The github-release action retrieves the changelog using the /repos/grafana/grafana/contents/CHANGELOG.md API
+    # endpoint.
     needs: setup
     uses: ./.github/workflows/github-release.yml
     with:
       version: ${{ needs.setup.outputs.version }}
       dry_run: ${{ needs.setup.outputs.dry_run == 'true' }}
-  publish_docs:
-    needs: setup
-    runs-on: ubuntu-latest
-    steps:
-    - run: |
-        echo publish docs for ${{ needs.setup.outputs.version }}
-        echo dry run: ${{ needs.setup.outputs.dry_run }}
   post_on_slack:
     needs: setup
     runs-on: ubuntu-latest

.github/workflows/release-pr.yml

@@ -34,12 +34,19 @@ permissions:
   pull-requests: write
 
 jobs:
+  push-changelog-to-main:
+    name: Create PR to main to update the changelog
+    uses: ./.github/workflows/changelog.yml
+    with:
+      version: ${{ inputs.version }}
+      latest: ${{ inputs.latest }}
+      dry_run: ${{ inputs.dry_run }}
+      target: main
   create-prs:
     name: Create Release PR
     runs-on: ubuntu-latest
     if: github.repository == 'grafana/grafana'
     steps:
-
       - name: Generate bot token
         id: generate_token
         uses: tibdex/github-app-token@b62528385c34dbc9f38e5f4225ac829252d1ea92