Implement automatic PR updates

.github/workflows/pr-auto-label.yaml

@@ -0,0 +1,30 @@
+name: "Automatically mark PRs to sync"
+
+on:
+    pull_request:
+        types:
+            - opened
+
+jobs:
+    labeler:
+        if: github.event.pull_request.user.type != 'Bot'
+        permissions:
+            pull-requests: write
+
+        runs-on: ubuntu-latest
+        steps:
+            - name: Add "sync" label to PR
+              run: gh pr edit "$PR_URL" --add-label sync --repo "$PR_REPO"
+              env:
+                GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+                PR_URL: ${{ github.event.pull_request.html_url }}
+                PR_REPO: ${{ github.repository }}
+
+            - name: Comment on PR to explain sync label
+              run: gh pr comment "$PR_URL" --body "This pull request has been marked to **automatically
+                sync** to its base branch. You can **disable** this behavior by removing the `sync`
+                label." --repo "$PR_REPO"
+              env:
+                GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+                PR_URL: ${{ github.event.pull_request.html_url }}
+                PR_REPO: ${{ github.repository }}

.github/workflows/pr-auto-merge.yml

@@ -0,0 +1,23 @@
+name: "Automatically enable auto-merge on PRs"
+
+on:
+    pull_request_target:
+        types:
+            - opened
+            - ready_for_review
+        branches:
+            - main
+
+jobs:
+    enable-automerge:
+        if: github.event.pull_request.draft == false
+        permissions:
+            pull-requests: write
+
+        runs-on: ubuntu-latest
+        steps:
+            - name: Enable auto-merge for the PR
+              run: gh pr merge "$PR_URL" --auto --squash
+              env:
+                GH_TOKEN: ${{ secrets.PR_AUTO_UPDATE_TOKEN }}
+                PR_URL: ${{ github.event.pull_request.html_url }}

.github/workflows/pr-auto-updater.yaml

@@ -0,0 +1,19 @@
+name: pr-auto-update
+on:
+    push: {}
+
+jobs:
+    pr-auto-update:
+        name: Automatic PR Updater
+        runs-on: ubuntu-latest
+        permissions:
+            pull-requests: write
+            contents: write
+        steps:
+            - uses: CSSUoB/[email protected]
+              env:
+                GITHUB_TOKEN: '${{ secrets.PR_AUTO_UPDATE_TOKEN }}'
+                PR_FILTER: 'labelled'
+                PR_LABELS: 'sync'
+                MERGE_CONFLICT_ACTION: 'label'
+                MERGE_CONFLICT_LABEL: 'conflict'