Add appending capabilities to the SimpleCommandLineArgsProvider

Adds the ability to add a list of command line arguments to the existing
ones.

Resolves #279

spring-cloud-task-batch/src/main/java/org/springframework/cloud/task/batch/partition/SimpleCommandLineArgsProvider.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.cloud.task.batch.partition;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import org.springframework.batch.item.ExecutionContext;
@@ -22,7 +23,8 @@ import org.springframework.cloud.task.repository.TaskExecution;
 import org.springframework.util.Assert;
 
 /**
- * Returns any command line arguments used with the {@link TaskExecution} provided.
+ * Returns any command line arguments used with the {@link TaskExecution} provided
+ * appended with any additional arguments configured.
  *
  * @author Michael Minella
  * @since 1.1.0
@@ -31,14 +33,38 @@ public class SimpleCommandLineArgsProvider implements CommandLineArgsProvider {
 
 	private final TaskExecution taskExecution;
 
+	private List<String> appendedArgs;
+
 	public SimpleCommandLineArgsProvider(TaskExecution taskExecution) {
 		Assert.notNull(taskExecution, "A taskExecution is required");
 
 		this.taskExecution = taskExecution;
 	}
 
+	/**
+	 * Additional command line args to be appended.
+	 *
+	 * @param appendedArgs list of arguments
+	 * @since 1.2
+	 */
+	public void setAppendedArgs(List<String> appendedArgs) {
+		this.appendedArgs = appendedArgs;
+	}
+
 	@Override
 	public List<String> getCommandLineArgs(ExecutionContext executionContext) {
-		return this.taskExecution.getArguments();
+
+		int listSize = this.taskExecution.getArguments().size() +
+				(this.appendedArgs != null ? this.appendedArgs.size() : 0);
+
+		List<String> args = new ArrayList<>(listSize);
+
+		args.addAll(this.taskExecution.getArguments());
+
+		if(this.appendedArgs != null) {
+			args.addAll(this.appendedArgs);
+		}
+
+		return args;
 	}
 }