CI: Move some Cirrus CI jobs to GitHub Actions

.github/workflows/main.yml

@@ -0,0 +1,93 @@
+# https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions
+
+name: Main
+on:
+  - pull_request # without merge conflicts
+  - push # branch or tag
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Linux
+          - job_name: Ubuntu 22.04 x64, DMD (latest)
+            os: ubuntu-22.04
+            host_dmd: dmd
+          - job_name: Ubuntu 22.04 x64, DMD (bootstrap)
+            os: ubuntu-22.04
+            host_dmd: dmd-2.079.0
+          - job_name: Ubuntu 22.04 x86, DMD (latest)
+            os: ubuntu-22.04
+            model: 32
+            host_dmd: dmd
+          - job_name: Ubuntu 22.04 x86, DMD (bootstrap)
+            os: ubuntu-22.04
+            model: 32
+            host_dmd: dmd-2.097.1
+          - job_name: Ubuntu 22.04 x64, LDC
+            os: ubuntu-22.04
+            host_dmd: ldc
+          - job_name: Ubuntu 22.04 x64, GDC
+            os: ubuntu-22.04
+            host_dmd: gdmd-9
+          # macOS
+          - job_name: macOS 13 x64, DMD (latest)
+            os: macos-13
+            host_dmd: dmd
+          - job_name: macOS 12 x64, DMD (bootstrap)
+            os: macos-12
+            # de-facto bootstrap version on OSX
+            # See: https://github.com/dlang/dmd/pull/13890
+            host_dmd: dmd-2.099.1
+    name: ${{ matrix.job_name }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 40
+    env:
+      # for ci/run.sh:
+      OS_NAME: ${{ startsWith(matrix.os, 'ubuntu') && 'linux' || (startsWith(matrix.os, 'macos') && 'darwin' || '') }}
+      MODEL: ${{ matrix.model || '64' }}
+      HOST_DMD: ${{ matrix.host_dmd }}
+      N: ${{ startsWith(matrix.os, 'macos') && '3' || '2' }}
+      FULL_BUILD: true
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 50
+      - name: Install prerequisites
+        run: ${{ runner.os == 'macOS' && 'ci/cirrusci.sh' || 'sudo -E ci/cirrusci.sh' }}
+      - name: Install host compiler
+        run: ci/run.sh install_host_compiler
+      - name: Set up repos
+        run: |
+          set -uexo pipefail
+          ln -s "$GITHUB_WORKSPACE" ../dmd
+
+          ref='${{ github.ref }}'
+          if [[ "$ref" =~ ^refs/pull/ ]]; then
+            # PR: clone the Phobos head with the same name as this DMD PR's target branch
+            # e.g., Phobos stable when targeting DMD stable
+            REPO_BRANCH="$GITHUB_BASE_REF"
+          elif [[ "$ref" =~ ^refs/(heads|tags)/(.*)$ ]]; then
+            # no PR: try to clone the Phobos head with the same name as this DMD head, falling back to master
+            # e.g., Phobos stable for a push to DMD stable, or Phobos v2.105.2 for DMD tag v2.105.2
+            REPO_BRANCH="${BASH_REMATCH[2]}"
+          else
+            echo "Error: unexpected GitHub ref '$ref'" >&2
+            exit 1
+          fi
+
+          ./ci/run.sh setup_repos "$REPO_BRANCH"
+      - name: Build
+        run: ci/run.sh build
+      - name: Test dmd
+        run: ci/run.sh test_dmd
+      - name: Test druntime
+        run: ci/run.sh test_druntime
+      - name: Test phobos
+        run: ci/run.sh test_phobos