Port from Travis-CI to GitHub Actions

Travis-CI no longer has a free tier (only a free trial). That was a
major reason we used Travis-CI, so that external contributors would be
able to run the CI on their forks. Iterating on a Travis config in a
personal repo was also quite convenient. The other reason was that
Travis-CI was safe to run even with untrusted code.

Since the introduction of the permissions field in workflows, GitHub
Actions appears safe to run untrusted code and has a free tier for
external contributors. GitHub Actions and Google Cloud Build are the
main contenders for a Kokoro replacement, but Cloud Build isn't safe for
untrusted code. Instead of migrating to Travis-CI.com from
Travis-CI.org, let's migrate to GitHub Actions and gain some familiarity.

I've really appreciated Travis-CI.org and have wanted to pay for it for
years but wasn't about to give it write permission to the repo. I'm
disappointed to migrate off it, now that the permissions issues have
been sorted out.

.github/workflows/testing.yml

@@ -0,0 +1,63 @@
+name: GitHub Actions Linux Testing
+
+on:
+  push:
+    branches:
+    - master
+    - 'v1.*'
+  pull_request:
+  schedule:
+  - cron: '54 19 * * SUN' # weekly at a "random" time
+
+permissions:
+  contents: read
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        jre: [8, 11]
+      fail-fast: false # Should swap to true if we grow a large matrix
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-java@v2
+      with:
+        java-version: ${{ matrix.jre }}
+        distribution: 'adopt'
+
+    - name: Gradle cache
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.gradle/caches
+          ~/.gradle/wrapper
+        key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+        restore-keys: |
+          ${{ runner.os }}-gradle-
+    - name: Maven cache
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.m2/repository
+          !~/.m2/repository/io/grpc
+        key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml', 'build.gradle') }}
+        restore-keys: |
+          ${{ runner.os }}-maven-
+    - name: Protobuf cache
+      uses: actions/cache@v2
+      with:
+        path: /tmp/protobuf-cache
+        key: ${{ runner.os }}-maven-${{ hashFiles('buildscripts/make_dependencies.sh') }}
+
+    - name: Build
+      run: buildscripts/kokoro/unix.sh
+    - name: Check for modified codegen
+      run: test -z "$(git status --porcelain)" || (git status && echo Error Working directory is not clean. Forget to commit generated files? && false)
+
+    - name: Coveralls
+      if: matrix.jre == 8 # Upload once, instead of for each job in the matrix
+      run: ./gradlew :grpc-all:coveralls -x compileJava
+    - name: Codecov
+      uses: codecov/codecov-action@v1

.gitignore

@@ -39,3 +39,6 @@ bin
 
 # ARM tests
 qemu-arm-static
+
+# Temporary output dir for artifacts
+mvn-artifacts

buildscripts/kokoro/unix.sh

@@ -57,13 +57,16 @@ if [[ -z "${SKIP_TESTS:-}" ]]; then
     exit 1
   fi
   # Run tests
-  ./gradlew build $GRADLE_FLAGS
+  ./gradlew build :grpc-all:jacocoTestReport $GRADLE_FLAGS
   pushd examples
   ./gradlew clean $GRADLE_FLAGS
   ./gradlew build $GRADLE_FLAGS
   # --batch-mode reduces log spam
   mvn verify --batch-mode
   popd
+  pushd examples/example-alts
+  ../gradlew build $GRADLE_FLAGS
+  popd
   pushd examples/example-hostname
   ../gradlew build $GRADLE_FLAGS
   mvn verify --batch-mode