added Docker Hub push automation

.travis.yml

@@ -1,7 +1,22 @@
 language: scala
+sudo: required
+
+services:
+  - docker
 
 scala:
   - 2.12.4
 
 script:
-  - ./test.sh
+  - ./test.sh
+
+# Improvement: move logic out of docker_push.sh into .travis.yml
+deploy:
+  provider: script
+  script: bash docker_push.sh
+  skip_cleanup: true
+#  on:
+#    all_branches: true
+#    tags: true / false  => has precendence over the branch condition
+#    condition: "foo == bar && baz==bat"
+#    repo: simplesteph/kafka-security-manager

build.sbt

@@ -39,3 +39,4 @@ parallelExecution in Test := false
 
 // Docker stuff
 dockerRepository := Some("simplesteph")
+dockerUpdateLatest := true

docker_push.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+./docker_build.sh
+
+docker_push(){
+    echo "Pushing tag $1 to docker hub"
+    docker tag "simplesteph/kafka-security-manager:latest" "simplesteph/kafka-security-manager:$1"
+    docker login -u "$DOCKER_USERNAME" -p "$DOCKER_PASSWORD";
+    docker push "simplesteph/kafka-security-manager:$1"
+}
+
+# TRAVIS_TAG: If the current build is for a git tag, this variable is set to the tag’s name.
+# TRAVIS_PULL_REQUEST_BRANCH: if the current job is a pull request, the name of the branch from which the PR originated.
+
+if [[ "$TRAVIS_PULL_REQUEST_BRANCH" == "" ]]; then
+    if [[ "$TRAVIS_TAG" =! "" ]]; then
+        # Tagging should trigger a release in Docker Hub, that's immutable.
+        echo "git tag action, push the tag"
+        docker_push "$TRAVIS_TAG-release"
+    elif [[ "$TRAVIS_BRANCH" == "master" ]]; then
+        # we push to latest when master is built and that's not a pull request
+        echo "master build, push to latest"
+        docker_push "latest"
+    elif [[ "$TRAVIS_BRANCH" ~= "v*" ]]; then
+        # this is a version branch and we push it.
+        echo "branch build, push to branch-latest"
+        docker_push "$TRAVIS_BRANCH-latest"
+    fi;
+fi;