Fix warnings in ArchiveCommand

- remove unnecessary imports
- fix NLS warnings
- add missing Javadoc tag

Bug: 410354
Change-Id: I2b78a2c0e92c740bed80558b17a2100c1c884416
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/ArchiveCommand.java

 import java.io.IOException;
 import java.io.OutputStream;
 import java.text.MessageFormat;
-import java.util.Collection;
-import java.util.Iterator;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
-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;
 import org.eclipse.jgit.internal.JGitText;
 				for (String sfx : fmt.suffixes())
 					if (filenameSuffix.endsWith(sfx))
 						return fmt;
-		return lookupFormat("tar");
+		return lookupFormat("tar"); //$NON-NLS-1$
 	}
 
 	private static Format<?> lookupFormat(String formatName) throws UnsupportedFormatException {
 	}
 
 	/**
-	 * Set the intended filename for the produced archive.
-	 * Currently the only effect is to determine the default
-	 * archive format when none is specified with
-	 * {@link #setFormat(String)}.
+	 * Set the intended filename for the produced archive. Currently the only
+	 * effect is to determine the default archive format when none is specified
+	 * with {@link #setFormat(String)}.
 	 *
 	 * @param filename
-	 *		intended filename for the archive
+	 *            intended filename for the archive
+	 * @return this
 	 */
 	public ArchiveCommand setFilename(String filename) {
 		int slash = filename.lastIndexOf('/');
 		int dot = filename.indexOf('.', slash + 1);
 
 		if (dot == -1)
-			this.suffix = "";
+			this.suffix = ""; //$NON-NLS-1$
 		else
 			this.suffix = filename.substring(dot);
 		return this;