ensure entire directories are copied for ADDs

Prior to this change, a mojo configuration like

```
<resource>
  <directory>some/directory</directory>
  <targetPath>/data</targetPath>
</resource>
```

would generate an `ADD /data /data` instruction but the `some/directory`
directory is never copied into the Docker build context directory, so
the actual build will fail.

With this change, the directory is copied to the build context
directory.

Note: it might seem weird that the `targetPath` is used as the directory
name to use *inside* the build context as opposed to just the target
path inside the container, but this is to mirror behavior when copying
individual files.

Fixes fabric8io#146.

src/main/java/com/spotify/docker/BuildMojo.java

@@ -46,6 +46,7 @@
 import org.apache.maven.project.MavenProject;
 import org.codehaus.plexus.component.configurator.expression.ExpressionEvaluationException;
 import org.codehaus.plexus.util.DirectoryScanner;
+import org.codehaus.plexus.util.FileUtils;
 import org.eclipse.jgit.api.errors.GitAPIException;
 
 import java.io.File;
@@ -604,6 +605,9 @@ private void createDockerFile(final String directory, final List<String> filesTo
       }
     }
 
+    getLog().debug("Writing Dockerfile:" + System.lineSeparator() +
+                   Joiner.on(System.lineSeparator()).join(commands));
+
     // this will overwrite an existing file
     Files.createDirectories(Paths.get(directory));
     Files.write(Paths.get(directory, "Dockerfile"), commands, UTF_8);
@@ -641,6 +645,11 @@ private List<String> copyResources(String destination) throws IOException {
       final String targetPath = resource.getTargetPath() == null ? "" : resource.getTargetPath();
 
       if (copyWholeDir) {
+        final Path destPath = Paths.get(destination, targetPath);
+        getLog().info(String.format("Copying dir %s -> %s", source, destPath));
+
+        Files.createDirectories(destPath);
+        FileUtils.copyDirectoryStructure(source, destPath.toFile());
         copiedPaths.add(separatorsToUnix(targetPath));
       } else {
         for (String included : includedFiles) {

src/test/java/com/spotify/docker/BuildMojoTest.java

@@ -21,6 +21,8 @@
 
 package com.spotify.docker;
 
+import com.google.common.collect.ImmutableList;
+
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.spotify.docker.client.AnsiProgressHandler;
@@ -229,6 +231,29 @@ public void testBuildWithGeneratedDockerfile() throws Exception {
                  Files.readAllLines(Paths.get("target/docker/Dockerfile"), UTF_8));
   }
 
+  public void testBuildGeneratedDockerFile_CopiesEntireDirectory() throws Exception {
+    final File pom = getTestFile("src/test/resources/pom-build-copy-entire-directory.xml");
+
+    final BuildMojo mojo = setupMojo(pom);
+    final DockerClient docker = mock(DockerClient.class);
+    mojo.execute(docker);
+
+    verify(docker).build(eq(Paths.get("target/docker")), eq("test-copied-directory"),
+        any(AnsiProgressHandler.class));
+
+    List<String> expectedDockerFileContents = ImmutableList.of(
+        "FROM busybox",
+        "ADD /data /data",
+        "ENTRYPOINT echo"
+    );
+
+    assertEquals("wrong dockerfile contents", expectedDockerFileContents,
+        Files.readAllLines(Paths.get("target/docker/Dockerfile"), UTF_8));
+
+    assertFileExists("target/docker/data/file.txt");
+    assertFileExists("target/docker/data/nested/file2");
+  }
+
   public void testBuildWithProfile() throws Exception {
     final File pom = getTestFile("src/test/resources/pom-build-with-profile.xml");
     assertNotNull("Null pom.xml", pom);

src/test/resources/copy-wholedir-data/file.txt

@@ -0,0 +1 @@
+Hello!

src/test/resources/copy-wholedir-data/nested/file2

@@ -0,0 +1 @@
+hi

src/test/resources/pom-build-copy-entire-directory.xml

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <name>Docker Maven Plugin Test Pom</name>
+  <groupId>com.spotify</groupId>
+  <artifactId>docker-maven-plugin-test</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+  <packaging>jar</packaging>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>com.spotify</groupId>
+        <artifactId>docker-maven-plugin</artifactId>
+        <version>0.1-SNAPSHOT</version>
+        <configuration>
+          <baseImage>busybox</baseImage>
+          <imageName>test-copied-directory</imageName>
+          <entryPoint>echo</entryPoint>
+          <resources>
+            <resource>
+              <targetPath>/data</targetPath>
+              <directory>src/test/resources/copy-wholedir-data</directory>
+            </resource>
+          </resources>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>