Add GitHub actions configuration

TravisCI is queing without ETA, and we're migrating most projects
anyway. Let's see how this goes.

.github/workflows/build-and-test.yml

@@ -0,0 +1,66 @@
+name: Continuous Integration
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '42 15 * * *'
+jobs:
+  build:
+    name: HHVM ${{matrix.hhvm}} - ${{matrix.os}}
+    strategy:
+      # Run tests on all OS's and HHVM versions, even if one fails
+      fail-fast: false
+      matrix:
+        os: [ ubuntu , macos ]
+        hhvm:
+          - '4.25'
+          - latest
+          - nightly
+    runs-on: ${{matrix.os}}-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Composer
+        run: .github/workflows/install-composer.sh --install-dir=${{runner.temp}}
+      - name: Install HHVM (apt)
+        if: matrix.os == 'ubuntu'
+        run: |
+          set -ex
+          export DEBIAN_FRONTEND=noninteractive
+          sudo apt-get update
+          sudo apt-get install -y software-properties-common apt-transport-https
+          sudo apt-key add .github/workflows/hhvm.gpg.key
+          if [ "${{matrix.hhvm}}" = "nightly" ]; then
+            sudo add-apt-repository https://dl.hhvm.com/ubuntu
+            sudo apt-get install -y hhvm-nightly
+          elif [ "${{matrix.hhvm}}" = "latest" ]; then
+            sudo add-apt-repository https://dl.hhvm.com/ubuntu
+            sudo apt-get install -y hhvm
+          else
+            DISTRO=$(lsb_release --codename --short)
+            sudo add-apt-repository \
+              "deb https://dl.hhvm.com/ubuntu ${DISTRO}-${{matrix.hhvm}} main"
+            sudo apt-get install -y hhvm
+          fi
+      - name: Install HHVM (brew)
+        if: matrix.os == 'macos'
+        run: |
+          brew tap hhvm/hhvm
+          if [ "${{matrix.hhvm}}" = "latest" ]; then
+            brew install hhvm
+          else
+            brew install hhvm-${{matrix.hhvm}}
+          fi
+      - name: Inspect HHVM and Hack versions
+        run: |
+          hhvm --version
+          hh_client --version
+      - name: Install project dependencies
+        run: php ${{runner.temp}}/composer.phar install
+      - name: Run autoloader
+        run: bin/hh-autoload
+      - name: Show autoload map
+        run: cat vendor/autoload.hack
+      - name: Typecheck
+        run: hh_client
+      - name: Run tests
+        run: vendor/bin/hacktest tests/*.hack

.github/workflows/hhvm.gpg.key

@@ -0,0 +1,36 @@
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+-----END PGP PUBLIC KEY BLOCK-----

.github/workflows/install-composer.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# From https://getcomposer.org/doc/faqs/how-to-install-composer-programmatically.md
+
+EXPECTED_CHECKSUM="$(wget -q -O - https://composer.github.io/installer.sig)"
+php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
+ACTUAL_CHECKSUM="$(php -r "echo hash_file('sha384', 'composer-setup.php');")"
+
+if [ "$EXPECTED_CHECKSUM" != "$ACTUAL_CHECKSUM" ]
+then
+    >&2 echo 'ERROR: Invalid installer checksum'
+    rm composer-setup.php
+    exit 1
+fi
+
+php composer-setup.php "$@"
+RESULT=$?
+rm composer-setup.php
+exit $RESULT