add workflow for creating backport PRs

Author: nzbr

.github/workflows/on_label.yml

@@ -0,0 +1,48 @@
+# Heavily inspired by https://github.com/NixOS/nixpkgs/blob/a698ac1214cd924d4394ca9cd2691618765aa03c/.github/workflows/backport.yml
+
+name: "On Backport Label"
+
+permissions:
+  pull-requests: write
+  contents: write
+
+on:
+  pull_request:
+    types:
+      - closed
+      - labeled
+
+jobs:
+  backport:
+    if: github.event.pull_request.labels && contains(join(github.event.pull_request.labels.*.name, ', '), 'backport ')
+    name: Backport PR 🔙
+    runs-on: ubuntu-latest
+    outputs:
+      created_pull_numbers: ${{ steps.backport.outputs.created_pull_numbers }}
+    steps:
+      - name: Check actor permissions
+        id: check-permissions
+        uses: prince-chrismc/check-actor-permissions-action@v3.0.2
+        with:
+          permission: write
+
+      - name: Checkout
+        uses: actions/checkout@v4.2.2
+
+      - name: Create backport PR
+        id: backport
+        uses: korthout/backport-action@v3.2.1
+        with:
+          merge_commits: "skip"
+          add_author_as_assignee: true
+          copy_requested_reviewers: true
+
+  trigger-ci:
+    name: Trigger CI on created branches 🚀
+    needs: backport
+    strategy:
+      matrix:
+        pr: fromJSON("[${{ needs.backport.outputs.created_branches }}]")
+    uses: ./.github/workflows/run_trigger_backport_ci.yml
+    with:
+      pr: ${{ matrix.pr }}

.github/workflows/on_push.yml

@@ -1,13 +1,36 @@
-name: "Push"
+name: "On Push"
 
 on:
   push:
     branches:
       - main
       - "release-*"
   pull_request: {}
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: "Pull Request Number"
+        required: false
+        default: ""
+      post_result:
+        description: "Post the result of the pipeline to the PR"
+        required: false
+        default: false
 
 jobs:
+  start-comment:
+    name: Post Start Comment 💬
+    if: ${{ inputs.post_result }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: thollander/actions-comment-pull-request@v3.0.1
+        with:
+          pr-number: ${{ inputs.pr_number || github.event.pull_request.number }}
+          comment-tag: ci-status
+          message: |
+            CI is currently running
+            [See the logs here](https://${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }})
+
   build:
     name: Build 🛠️
     uses: ./.github/workflows/run_build.yml
@@ -55,3 +78,28 @@ jobs:
           }
 
           exit $exit
+
+  finish-comment:
+    name: Post Finish Comment 💬
+    if: ${{ inputs.post_result }}
+    needs:
+      - start-comment
+      - build
+      - checks
+      - tests
+      - docs
+    runs-on: ubuntu-latest
+    steps:
+      - uses: thollander/actions-comment-pull-request@v3.0.1
+        with:
+          pr-number: ${{ inputs.pr_number || github.event.pull_request.number }}
+          comment-tag: ci-status
+          mode: update
+          message: |
+            CI has finished:
+            - 📋 Checks: ${{ needs.checks.result && '✅' || '❌' }}
+            - 🛠️ Build: ${{ needs.build.result && '✅' || '❌' }}
+            - 🧪 Tests: ${{ needs.tests.result && '✅' || '❌' }}
+            - 📕 Docs: ${{ needs.docs.result && '✅' || '❌' }}
+
+            [See the logs here](https://${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }})

.github/workflows/run_trigger_backport_ci.yml

@@ -0,0 +1,28 @@
+name: Run Backport CI
+
+on:
+  workflow_call:
+    inputs:
+      pr:
+        required: true
+        type: number
+
+jobs:
+  trigger-ci:
+    name: Trigger CI on Backport Branch 🚀
+    runs-on: ubuntu-latest
+    steps:
+      - name: Find branch
+        id: find_branch
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          branch=$(gh pr view ${{ inputs.pr }} --json headRefName -q .headRefName)
+          echo "branch=$branch" >> $GITHUB_OUTPUT
+
+      - name: Workflow Dispatch
+        uses: benc-uk/workflow-dispatch@v1.2.4
+        with:
+          workflow: "on_push.yml"
+          ref: ${{ steps.find_branch.outputs.branch }}
+          inputs: '{"post_result": true}'