Add redirects label workflow (#5079)

* Add workflow for checking for redirects

* Add mergify pull request rules to help with handling redirect labels

* Split workflow to check for file deletions on PR opened and PR sync

* Add newline at eof

* remove extra spaces

* add newline at eof

* fix typo

* Move github variables into environment variables

Author: timngyn

.github/workflows/check_for_redirects.yml

@@ -0,0 +1,56 @@
+name: Redirects Workflow
+on:
+  pull_request:
+    branches: [main]
+    types: [opened, synchronize, labeled]
+env:
+  DIFF_DIRECTORIES: 'src/pages src/fragments'
+jobs:
+  onPrOpen:
+    name: Check if redirects are needed on PR opened
+    runs-on: ubuntu-latest
+    if: github.event.action == 'opened'
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+        with:
+          # Minimal depth 2 so we can checkout the commit before possible merge commit.
+          fetch-depth: 2
+      - name: Get count of deleted files
+        env:
+          GITHUB_PULL_REQUEST_HEAD_SHA: ${{ github.pull_request.head.sha }}
+        run: |
+          git fetch origin main
+          echo "DELETED_FILES_ON_OPENED=$(git diff --name-status --diff-filter=D origin/main -- ${{ env.DIFF_DIRECTORIES }} ${{ env.GITHUB_PULL_REQUEST_HEAD_SHA }} -- ${{ env.DIFF_DIRECTORIES }} | wc -l)" >> $GITHUB_ENV
+          echo "Deleted file count: ${{ env.DELETED_FILES_ON_OPENED }}"
+      - name: Fail status check if there are deleted files
+        if: ${{ env.DELETED_FILES_ON_OPENED > 0 }}
+        run: exit 1
+  onPrSync:
+    name: Check if redirects are needed on PR sync
+    runs-on: ubuntu-latest
+    if: github.event.action == 'synchronize'
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+        with:
+          # Minimal depth 2 so we can checkout the commit before possible merge commit.
+          fetch-depth: 2
+      - name: Get count of deleted files from last sync
+        env:
+          GITHUB_EVENT_BEFORE: ${{ github.event.before }}
+          GITHUB_EVENT_AFTER: ${{ github.event.after }}
+        run: |
+          git fetch origin ${{ github.event.before }} --depth=1
+          echo "DELETED_FILES_ON_SYNC=$(git diff --name-status --diff-filter=D ${{ env.GITHUB_EVENT_BEFORE}} -- ${{ env.DIFF_DIRECTORIES }} ${{ env.GITHUB_EVENT_AFTER }} -- ${{ env.DIFF_DIRECTORIES }} | wc -l)" >> $GITHUB_ENV
+          echo "Deleted file count: ${{ env.DELETED_FILES_ON_SYNC }}"
+      - name: Fail status check if there are deleted files
+        if: ${{ env.DELETED_FILES_ON_SYNC > 0 }}
+        run: exit 1
+  failStatusCheck:
+    name: Fail status check if redirects have not been added
+    runs-on: ubuntu-latest
+    if: contains(github.event.pull_request.labels.*.name, 'redirects-needed')
+    steps:
+      - name: Exit with error
+        run: exit 1

.mergify.yml

@@ -0,0 +1,26 @@
+pull_request_rules:
+  - name: Ask PR author what redirects are needed
+    conditions:
+      - label="redirects-needed"
+    actions:
+      comment:
+        message: |
+          @{{author}}, since a file was deleted from the `src/pages` and/or `src/fragments` directories, redirects might need to be set up so these previous pages do not 404. If redirects are needed, please answer these questions for each redirect that is needed:
+
+          - What is the source address of the redirect? (Where are you trying to redirect from?)
+
+          - What is the target address of the redirect? (Where are you trying to redirect to?)
+
+          - Type of redirect? 301 - permanent redirect or 302 - temporary redirect? (More info on Amplify Hosting redirects here: https://docs.aws.amazon.com/amplify/latest/userguide/redirects.html)
+      label:
+        remove:
+          - 'redirects-added'
+  - name: Add redirects-needed label if status checks fail
+    conditions:
+      - or:
+        - check-failure="Check if redirects are needed on PR opened"
+        - check-failure="Check if redirects are needed on PR sync"
+    actions:
+      label:
+        add:
+          - 'redirects-needed'