Migrate CI to Github Actions

.github/workflows/ci.yml

@@ -0,0 +1,51 @@
+---
+
+name: ci
+
+on:
+  pull_request:
+
+  push:
+    branches:
+      - master
+
+jobs:
+  test:
+    runs-on: ubuntu-20.04
+
+    timeout-minutes: 15
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        ruby: [2.5.8, 2.6.6, 2.7.1, jruby-9.2.11.1]
+
+    env:
+      BUNDLE_PATH: vendor/bundle
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.7.2
+          bundler: none
+
+      - name: Install a specific rubygems version
+        run: gem update --system 3.2.0.rc.1
+
+      - name: Install a specific bundler version
+        run: gem install bundler -v 2.1.4
+
+      - name: Restore cached dependencies
+        uses: actions/cache@v2
+        with:
+          path: ${{ env.BUNDLE_PATH }}
+          key: gems-${{ matrix.ruby }}-${{ hashFiles('current_gemfile.lock') }}
+
+      - name: Install dependencies
+        run: bundle install --jobs 3
+
+      - name: Run tests
+        run: bundle exec rake

README.md

@@ -3,7 +3,7 @@
 [Arbre][docs] makes it easy to generate HTML directly in Ruby. This gem was extracted from [Active Admin](https://github.com/activeadmin/active_admin).
 
 [![Version         ][rubygems_badge]][rubygems]
-[![Travis CI       ][travis_badge]][travis]
+[![Github Actions  ][actions_badge]][actions]
 [![Tidelift        ][tidelift_badge]][tidelift]
 
 ## Goals
@@ -33,8 +33,8 @@ Tidelift will coordinate the fix and disclosure.
 
 [rubygems_badge]: http://img.shields.io/gem/v/arbre.svg
 [rubygems]: https://rubygems.org/gems/arbre
-[travis_badge]: http://img.shields.io/travis/activeadmin/arbre/master.svg
-[travis]: https://travis-ci.org/activeadmin/arbre
+[actions_badge]: https://github.com/activeadmin/arbre/workflows/ci/badge.svg
+[actions]: https://github.com/activeadmin/arbre/actions
 [tidelift_badge]: https://tidelift.com/badges/github/activeadmin/arbre
 [tidelift]: https://tidelift.com/subscription/pkg/rubygems-arbre?utm_source=rubygems-arbre&utm_medium=referral&utm_campaign=readme