Add .gitlab-ci.yml

.gitlab-ci.yml

+# Use Maven 3.5 and JDK8
+image: maven:3.5-jdk-8
+
+variables:
+  # This will supress any download for dependencies and plugins or upload messages which would clutter the console log.
+  # `showDateTime` will show the passed time in milliseconds. You need to specify `--batch-mode` to make this work.
+  MAVEN_OPTS: "-Dmaven.repo.local=.m2/repository -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=WARN -Dorg.slf4j.simpleLogger.showDateTime=true -Djava.awt.headless=true"
+  # As of Maven 3.3.0 instead of this you may define these options in `.mvn/maven.config` so the same config is used
+  # when running from the command line.
+  # `installAtEnd` and `deployAtEnd`are only effective with recent version of the corresponding plugins.
+  MAVEN_CLI_OPTS: "--batch-mode --errors --fail-at-end --show-version -DinstallAtEnd=true -DdeployAtEnd=true"
+
+# Cache downloaded dependencies and plugins between builds.
+# To keep cache across branches add 'key: "$CI_JOB_REF_NAME"'
+cache:
+  paths:
+    - .m2/repository
+
+# This will only validate and compile stuff and run e.g. maven-enforcer-plugin.
+# Because some enforcer rules might check dependency convergence and class duplications
+# we use `test-compile` here instead of `validate`, so the correct classpath is picked up.
+compile:
+  stage: build
+  script:
+    - 'mvn $MAVEN_CLI_OPTS test-compile'
+
+# Run `verify`.
+# See https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html
+verify:
+  stage: test
+  script:
+    - 'mvn $MAVEN_CLI_OPTS verify'
+  artifacts:
+    paths:
+    - target/*.jar
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