Allow to build image with multiple tags

src/functTest/groovy/com/bmuschko/gradle/docker/tasks/image/DockerBuildImageFunctionalTest.groovy

@@ -1,9 +1,7 @@
 package com.bmuschko.gradle.docker.tasks.image
 
 import com.bmuschko.gradle.docker.AbstractFunctionalTest
-import com.bmuschko.gradle.docker.TestPrecondition
 import org.gradle.testkit.runner.BuildResult
-import spock.lang.Requires
 import spock.lang.Unroll
 
 class DockerBuildImageFunctionalTest extends AbstractFunctionalTest {
@@ -55,13 +53,26 @@ class DockerBuildImageFunctionalTest extends AbstractFunctionalTest {
         gradleTaskDefinition << [imageCreationWithBuildArgs(), imageCreationWithLabelParameter()]
     }
 
+    def "can build image with multiple tags"() {
+        buildFile << buildImageWithTags()
+
+        when:
+        BuildResult result = build('buildImageWithTags', 'buildImageWithTag')
+
+        then:
+        result.output.contains("Using tags 'test/image:123', 'registry.com:5000/test/image:123' for image.")
+        result.output.contains("Using tag 'test/image:123' for image.")
+    }
+
+
+
     private String imageCreation() {
         """
             import com.bmuschko.gradle.docker.tasks.image.Dockerfile
             import com.bmuschko.gradle.docker.tasks.image.DockerBuildImage
 
             task dockerfile(type: Dockerfile) {
-                from 'ubuntu:12.04'
+                from 'alpine'
             }
 
             task buildImage(type: DockerBuildImage) {
@@ -78,7 +89,7 @@ class DockerBuildImageFunctionalTest extends AbstractFunctionalTest {
             import com.bmuschko.gradle.docker.tasks.image.DockerInspectImage
 
             task dockerfile(type: Dockerfile) {
-                from 'ubuntu:12.04'
+                from 'alpine'
 
                 arg('arg1')
                 arg('arg2')
@@ -106,7 +117,7 @@ class DockerBuildImageFunctionalTest extends AbstractFunctionalTest {
             import com.bmuschko.gradle.docker.tasks.image.DockerInspectImage
 
             task dockerfile(type: Dockerfile) {
-                from 'ubuntu:12.04'
+                from 'alpine'
             }
 
             task buildImage(type: DockerBuildImage) {
@@ -121,4 +132,27 @@ class DockerBuildImageFunctionalTest extends AbstractFunctionalTest {
             }
         """
     }
+
+    private String buildImageWithTags() {
+        """
+            import com.bmuschko.gradle.docker.tasks.image.Dockerfile
+            import com.bmuschko.gradle.docker.tasks.image.DockerBuildImage
+
+            task dockerfile(type: Dockerfile) {
+                from 'alpine'
+            }
+
+            task buildImageWithTags(type: DockerBuildImage) {
+                dependsOn dockerfile
+                inputDir = file("build/docker")
+                tags = ['test/image:123', 'registry.com:5000/test/image:123']
+            }
+
+            task buildImageWithTag(type: DockerBuildImage) {
+                dependsOn dockerfile
+                inputDir = file("build/docker")
+                tag = 'test/image:123'
+            }
+        """
+    }
 }

src/main/groovy/com/bmuschko/gradle/docker/tasks/image/DockerBuildImage.groovy

@@ -36,11 +36,20 @@ class DockerBuildImage extends AbstractDockerRemoteApiTask implements RegistryCr
     @Optional
     File dockerFile
 
+    /**
+     * Tags for image.
+     */
+    @Input
+    @Optional
+    Set<String> tags = []
+
     /**
      * Tag for image.
+     * @deprecated use {@link #tags}
      */
     @Input
     @Optional
+    @Deprecated
     String tag
 
     @Input
@@ -95,9 +104,13 @@ class DockerBuildImage extends AbstractDockerRemoteApiTask implements RegistryCr
             buildImageCmd = dockerClient.buildImageCmd(getInputDir())
         }
 
-        if (getTag()) {
+        if(getTag()) {
             logger.quiet "Using tag '${getTag()}' for image."
             buildImageCmd.withTag(getTag())
+        } else if (getTags()) {
+            def tagListString = getTags().collect {"'${it}'"}.join(", ")
+            logger.quiet "Using tags ${tagListString} for image."
+            buildImageCmd.withTags(getTags())
         }
 
         if (getNoCache()) {