Cleanup imports and javadocs in ArchiveCommand

Change-Id: Icb1cd177e791cc646636a88c67fd9399dfc7030c

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/archive/ArchiveCommand.java

@@ -42,12 +42,10 @@
  */
 package org.eclipse.jgit.pgm.archive;
 
-import java.lang.String;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.EnumMap;
 import java.util.Map;
-import java.text.MessageFormat;
 
 import org.apache.commons.compress.archivers.ArchiveOutputStream;
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
@@ -55,6 +53,7 @@ import org.apache.commons.compress.archivers.tar.TarArchiveOutputStream;
 import org.apache.commons.compress.archivers.tar.TarConstants;
 import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
 import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream;
+import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.GitCommand;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
@@ -106,7 +105,10 @@ public class ArchiveCommand extends GitCommand<OutputStream> {
 	 * the --format= option)
 	 */
 	public static enum Format {
+		/** Zip format */
 		ZIP,
+
+		/** Posix TAR-format */
 		TAR
 	}
 
@@ -244,6 +246,7 @@ public class ArchiveCommand extends GitCommand<OutputStream> {
 	 * @param tree
 	 *            the tag, commit, or tree object to produce an archive for
 	 * @return this
+	 * @throws IOException
 	 */
 	public ArchiveCommand setTree(ObjectId tree) throws IOException {
 		final RevWalk rw = new RevWalk(walk.getObjectReader());