Allow users to specify additional command line args for creating drui…

…d package (apache#3812)

* Allow users to specify additional command line args for creating tar balls

This PR allows users to specify additional command line options to the
pull deps command while creating druid distribution.
e.g. To also package graphite-emitter in druid tarball one can run -
mvn package -Ddruid.distribution.pulldeps.opts='-c
io.druid.extensions.contrib:graphite-emitter'

* Set default to --clean instead of blank value

distribution/pom.xml

@@ -39,6 +39,10 @@
             <version>${project.parent.version}</version>
         </dependency>
     </dependencies>
+    <properties>
+        <!-- the default value is a repeated flag from the command line, since blank value is not allowed -->
+        <druid.distribution.pulldeps.opts>--clean</druid.distribution.pulldeps.opts>
+    </properties>
 
     <build>
         <plugins>
@@ -100,6 +104,7 @@
                                 <argument>io.druid.extensions:mysql-metadata-storage</argument>
                                 <argument>-c</argument>
                                 <argument>io.druid.extensions:postgresql-metadata-storage</argument>
+                                <argument>${druid.distribution.pulldeps.opts}</argument>
                             </arguments>
                         </configuration>
                     </execution>

services/src/main/java/io/druid/cli/PullDependencies.java

@@ -241,7 +241,8 @@ public void run()
 
     try {
       log.info("Start downloading dependencies for extension coordinates: [%s]", coordinates);
-      for (final String coordinate : coordinates) {
+      for (String coordinate : coordinates) {
+        coordinate = coordinate.trim();
         final Artifact versionedArtifact = getArtifact(coordinate);
 
         File currExtensionDir = new File(extensionsDir, versionedArtifact.getArtifactId());