flag to update latest tag

src/main/scala/com/typesafe/sbt/packager/docker/DockerPlugin.scala

@@ -92,7 +92,7 @@ trait DockerPlugin extends Plugin with UniversalPlugin {
     }
   }
 
-  def publishLocalDocker(context: File, tag: String, log: Logger): Unit = {
+  def publishLocalDocker(context: File, tag: String, latest: Boolean, log: Logger): Unit = {
     val cmd = Seq("docker", "build", "--force-rm", "-t", tag, ".")
     val cwd = context.getParentFile
 
@@ -105,6 +105,15 @@ trait DockerPlugin extends Plugin with UniversalPlugin {
       throw new RuntimeException("Nonzero exit value: " + ret)
     else
       log.info("Built image " + tag)
+
+    if (latest) {
+      val name = tag.substring(0, tag.lastIndexOf(":")) + ":latest"
+      val latestCmd = Seq("docker", "tag", tag, name)
+      Process(latestCmd).! match {
+        case 0 => log.info("Update Latest from image" + tag)
+        case n => sys.error("Failed to run docker tag")
+      }
+    }
   }
 
   def publishDocker(tag: String, log: Logger): Unit = {
@@ -152,6 +161,7 @@ trait DockerPlugin extends Plugin with UniversalPlugin {
     packageName in Docker <<= packageName,
     executableScriptName in Docker <<= executableScriptName,
     dockerRepository := None,
+    dockerUpdateLatest := false,
     sourceDirectory in Docker <<= sourceDirectory apply (_ / "docker"),
     target in Docker <<= target apply (_ / "docker"),
 
@@ -180,13 +190,17 @@ trait DockerPlugin extends Plugin with UniversalPlugin {
         (repo, name, version) =>
           repo.map(_ + "/").getOrElse("") + name + ":" + version
       },
-      publishLocal <<= (dockerGenerateConfig, dockerGenerateContext, dockerTarget, streams) map {
-        (config, _, target, s) =>
-          publishLocalDocker(config, target, s.log)
+      publishLocal <<= (dockerGenerateConfig, dockerGenerateContext, dockerTarget, dockerUpdateLatest, streams) map {
+        (config, _, target, updateLatest, s) =>
+          publishLocalDocker(config, target, updateLatest, s.log)
       },
-      publish <<= (publishLocal, dockerTarget, streams) map {
-        (_, target, s) =>
+      publish <<= (publishLocal, dockerTarget, dockerUpdateLatest, streams) map {
+        (_, target, updateLatest, s) =>
           publishDocker(target, s.log)
+          if (updateLatest) {
+            val name = target.substring(0, target.lastIndexOf(":")) + ":latest"
+            publishDocker(name, s.log)
+          }
       }
     ))
 }

src/main/scala/com/typesafe/sbt/packager/docker/Keys.scala

@@ -14,6 +14,7 @@ trait DockerKeys {
   val dockerExposedPorts = SettingKey[Seq[Int]]("dockerExposedPorts", "Ports exposed by Docker image")
   val dockerExposedVolumes = SettingKey[Seq[String]]("dockerExposedVolumes", "Volumes exposed by Docker image")
   val dockerRepository = SettingKey[Option[String]]("dockerRepository", "Repository for published Docker image")
+  val dockerUpdateLatest = SettingKey[Boolean]("dockerUpdateLatest", "Set to update latest tag")
 }
 
 object Keys extends DockerKeys {

src/sbt-test/docker/update-latest/build.sbt

@@ -0,0 +1,12 @@
+import com.typesafe.sbt.SbtNativePackager._
+import NativePackagerKeys._
+
+packageArchetype.java_application
+
+name := "docker-test"
+
+version := "0.1.0"
+
+maintainer := "Gary Coady <[email protected]>"
+
+dockerUpdateLatest := true

src/sbt-test/docker/update-latest/project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % sys.props("project.version"))

src/sbt-test/docker/update-latest/src/main/scala/Main.scala

@@ -0,0 +1,3 @@
+object Main extends App {
+  println("Hello world")
+}

src/sbt-test/docker/update-latest/test

@@ -0,0 +1,3 @@
+# Generate the Docker image locally
+> docker:publishLocal
+$ exec bash -c 'docker run docker-test:latest | grep -q "Hello world"'

src/sphinx/DetailedTopics/docker.rst

@@ -62,6 +62,8 @@ Publishing Settings
   ``dockerRepository``
     The repository to which the image is pushed when the ``docker:publish`` task is run. This should be of the form ``[username]`` (assumes use of the ``index.docker.io`` repository) or ``[repository.host]/[username]``.
 
+  ``dockerUpdateLatest``
+    The flag to automatic update the latest tag when the ``docker:publish`` task is run. Default value is ``FALSE``.
 
 Tasks
 -----