Allow to list tags with org.eclipse.jgit.pgm.Tag

Change-Id: I79c284a720935814aef9767156106833f983bb8b

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Tag.java

 
 package org.eclipse.jgit.pgm;
 
+import java.util.List;
+
 import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.ListTagCommand;
 import org.eclipse.jgit.api.TagCommand;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.revwalk.RevTag;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.kohsuke.args4j.Argument;
 import org.kohsuke.args4j.Option;
 	@Option(name = "-m", metaVar = "metaVar_message", usage = "usage_tagMessage")
 	private String message = "";
 
-	@Argument(index = 0, required = true, metaVar = "metaVar_name")
+	@Argument(index = 0, metaVar = "metaVar_name")
 	private String tagName;
 
 	@Argument(index = 1, metaVar = "metaVar_object")
 	@Override
 	protected void run() throws Exception {
 		Git git = new Git(db);
-		TagCommand command = git.tag().setForceUpdate(force).setMessage(message).setName(tagName);
+		if (tagName != null) {
+			TagCommand command = git.tag().setForceUpdate(force)
+					.setMessage(message).setName(tagName);
 
-		if (object != null) {
-			RevWalk walk = new RevWalk(db);
-			command.setObjectId(walk.parseAny(object));
-		}
+			if (object != null) {
+				RevWalk walk = new RevWalk(db);
+				command.setObjectId(walk.parseAny(object));
+			}
 
-		command.call();
+			command.call();
+		} else {
+			ListTagCommand command = git.tagList();
+			List<RevTag> list = command.call();
+			for (RevTag revTag : list) {
+				out.println(revTag.getTagName());
+			}
+		}
 	}
 }