Added legacy build.

.github/workflows/legacy.yml

@@ -0,0 +1,60 @@
+name: Legacy Build
+
+on:
+  push:
+    branches: [ legacy ]
+
+  pull_request:
+    branches: [ legacy ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php:
+          - 7.4
+          - 8.0
+          - 8.1
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Validate composer.json and composer.lock
+        run: composer validate --strict
+
+      - name: Cache Composer packages
+        id: composer-cache
+        uses: actions/cache@v2
+        with:
+          path: vendor
+          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-php-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress
+
+      - name: Run test suite
+        run: composer run-script test
+
+  release:
+    if: startsWith(github.ref, 'refs/tags/1')
+    runs-on: ubuntu-latest
+    needs: [build]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Build package
+        run: make build
+
+      - name: Rename package to current tag
+        run: mv build.zip gitlist-${{ github.ref_name }}.zip
+
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        with:
+          generate_release_notes: true
+          files: gitlist-${{ github.ref_name }}.zip