Adopt GitHub Actions in gax-java: unit tests and linkage monitor

.github/workflows/ci.yaml

@@ -0,0 +1,34 @@
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+name: ci
+jobs:
+  units:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [7, 8, 11]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v1
+        with:
+          java-version: ${{ matrix.java }}
+      - run: java -version
+      - run: .kokoro/build.sh
+        env:
+          JOB_TYPE: test
+      - name: coverage
+        uses: codecov/codecov-action@v1
+        with:
+          name: actions ${{ matrix.java }}
+  linkage-monitor:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v1
+        with:
+          java-version: 8
+      - run: java -version
+      - run: .kokoro/linkage-monitor.sh

.kokoro/build.sh

@@ -15,7 +15,9 @@
 
 set -eo pipefail
 
-cd github/gax-java/
+scriptDir=$(realpath $(dirname "${BASH_SOURCE[0]}"))
+## cd to the parent directory, i.e. the root of the git repo
+cd ${scriptDir}/..
 
 # Print out Java
 java -version
@@ -24,4 +26,7 @@ echo $JOB_TYPE
 ./gradlew assemble
 ./gradlew build install
 
-bash $KOKORO_GFILE_DIR/codecov.sh
+if [ "${REPORT_COVERAGE}" == "true" ]
+then
+  bash ${KOKORO_GFILE_DIR}/codecov.sh
+fi

.kokoro/linkage-monitor.sh

@@ -17,7 +17,9 @@ set -eo pipefail
 # Display commands being run.
 set -x
 
-cd github/gax-java/
+scriptDir=$(realpath $(dirname "${BASH_SOURCE[0]}"))
+## cd to the parent directory, i.e. the root of the git repo
+cd ${scriptDir}/..
 
 # Print out Java version
 java -version