Refactoring to batch (#181)

The rationale of this pull request is to

* have more maintainable and granular code
* not maintain the custom made job engine
* allow the users to customize the defaults of the releaser more easy
* allow the users to create their own steps without the need to change any existing code
* allow the users to fully change the flows and tasks logic
* abstract underlying batch mechanism (Spring Batch) so it doesn't leak to production code
* allow parallelization of the release process and release tasks

releaser-spring/src/main/java/releaser/internal/tasks/release/PushChangesReleaseTask.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package releaser.internal.tasks.release;
+
+import releaser.internal.Releaser;
+import releaser.internal.spring.Arguments;
+import releaser.internal.spring.ExecutionResult;
+import releaser.internal.tasks.ReleaseReleaserTask;
+
+public class PushChangesReleaseTask implements ReleaseReleaserTask {
+
+	/**
+	 * Order of this task. The higher value, the lower order.
+	 */
+	public static final int ORDER = 60;
+
+	private final Releaser releaser;
+
+	public PushChangesReleaseTask(Releaser releaser) {
+		this.releaser = releaser;
+	}
+
+	@Override
+	public String name() {
+		return "push";
+	}
+
+	@Override
+	public String shortName() {
+		return "p";
+	}
+
+	@Override
+	public String header() {
+		return "PUSHING CHANGES";
+	}
+
+	@Override
+	public String description() {
+		return "Push the commits";
+	}
+
+	@Override
+	public ExecutionResult runTask(Arguments args) {
+		this.releaser.pushCurrentBranch(args.project);
+		return ExecutionResult.success();
+	}
+
+	@Override
+	public int getOrder() {
+		return PushChangesReleaseTask.ORDER;
+	}
+
+}