DEV: Add GitHub Actions workflow for testing migrations

This workflow runs only for code underneath the `migrations/` directory. The usual test workflow is skipped for migrations because running frontend and backend tests is a waste of time and resources when only migrations are changed.

.github/workflows/migration-tests.yml

@@ -0,0 +1,126 @@
+name: Migration Tests
+
+on:
+  pull_request:
+    paths:
+      - "migrations/**"
+  push:
+    branches:
+      - main
+      - stable
+    paths:
+      - "migrations/**"
+
+concurrency:
+  group: migration-tests-${{ format('{0}-{1}', github.head_ref || github.run_number, github.job) }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  tests:
+    name: Ruby ${{ matrix.ruby }}
+    runs-on: 'ubuntu-latest'
+    container: discourse/discourse_test:slim
+    timeout-minutes: 20
+
+    env:
+      RAILS_ENV: test
+      PGUSER: discourse
+      PGPASSWORD: discourse
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        ruby: ["3.2"]
+
+    steps:
+      - name: Set working directory owner
+        run: chown root:root .
+
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - name: Setup Git
+        run: |
+          git config --global user.email "ci@ci.invalid"
+          git config --global user.name "Discourse CI"
+
+      - name: Start redis
+        run: |
+          redis-server /etc/redis/redis.conf &
+
+      - name: Start Postgres
+        run: |
+          chown -R postgres /var/run/postgresql
+          sudo -E -u postgres script/start_test_db.rb
+          sudo -u postgres psql -c "CREATE ROLE $PGUSER LOGIN SUPERUSER PASSWORD '$PGPASSWORD';"
+
+      - name: Bundler cache
+        uses: actions/cache@v3
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-${{ matrix.ruby }}-gem-${{ hashFiles('**/Gemfile.lock') }}
+          restore-keys: ${{ runner.os }}-${{ matrix.ruby }}-gem-
+
+      - name: Setup gems
+        run: |
+          gem install bundler --conservative -v $(awk '/BUNDLED WITH/ { getline; gsub(/ /,""); print $0 }' Gemfile.lock)
+          bundle config --local path vendor/bundle
+          bundle config --local deployment true
+          bundle config --local without development
+          bundle install --jobs 4
+          bundle clean
+
+      - name: Get yarn cache directory
+        id: yarn-cache-dir
+        run: echo "dir=$(yarn cache dir)" >> $GITHUB_OUTPUT
+
+      - name: Yarn cache
+        uses: actions/cache@v3
+        id: yarn-cache
+        with:
+          path: ${{ steps.yarn-cache-dir.outputs.dir }}
+          key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+          restore-keys: ${{ runner.os }}-yarn-
+
+      - name: Yarn install
+        run: yarn install --frozen-lockfile
+
+      - name: Fetch app state cache
+        uses: actions/cache@v3
+        id: app-cache
+        with:
+          path: tmp/app-cache
+          key: >-
+            ${{ runner.os }}-
+            ${{ hashFiles('.github/workflows/tests.yml') }}-
+            ${{ hashFiles('db/**/*', 'plugins/**/db/**/*') }}-
+
+      - name: Restore database from cache
+        if: steps.app-cache.outputs.cache-hit == 'true'
+        run: psql --quiet -o /dev/null -f tmp/app-cache/cache.sql postgres
+
+      - name: Restore uploads from cache
+        if: steps.app-cache.outputs.cache-hit == 'true'
+        run: rm -rf public/uploads && cp -r tmp/app-cache/uploads public/uploads
+
+      - name: Create and migrate database
+        if: steps.app-cache.outputs.cache-hit != 'true'
+        run: |
+          bin/rake db:create
+          bin/rake db:migrate
+
+      - name: Dump database for cache
+        if: steps.app-cache.outputs.cache-hit != 'true'
+        run: mkdir -p tmp/app-cache && pg_dumpall > tmp/app-cache/cache.sql
+
+      - name: Dump uploads for cache
+        if: steps.app-cache.outputs.cache-hit != 'true'
+        run: rm -rf tmp/app-cache/uploads && cp -r public/uploads tmp/app-cache/uploads
+
+      - name: RSpec
+        run: bin/rspec migrations/spec/

.github/workflows/tests.yml

@@ -2,11 +2,15 @@ name: Tests
 
 on:
   pull_request:
+    paths-ignore:
+      - "migrations/**"
   push:
     branches:
       - main
       - beta
       - stable
+    paths-ignore:
+      - "migrations/**"
 
 concurrency:
   group: tests-${{ format('{0}-{1}', github.head_ref || github.run_number, github.job) }}