Use more specific exception for cases when there are no files to be archived

This closes #51

Author: vehovsky

src/main/java/org/codehaus/plexus/archiver/dir/DirectoryArchiver.java

@@ -23,6 +23,7 @@
 import org.codehaus.plexus.archiver.ArchiveEntry;
 import org.codehaus.plexus.archiver.ArchiverException;
 import org.codehaus.plexus.archiver.ResourceIterator;
+import org.codehaus.plexus.archiver.exceptions.EmptyArchiveException;
 import org.codehaus.plexus.archiver.util.ArchiveEntryUtils;
 import org.codehaus.plexus.archiver.util.ResourceUtils;
 import org.codehaus.plexus.components.io.attributes.SymlinkUtils;
@@ -53,7 +54,7 @@ public void execute()
         final ResourceIterator iter = getResources();
         if ( !iter.hasNext() )
         {
-            throw new ArchiverException( "You must set at least one file." );
+            throw new EmptyArchiveException( "You must set at least one file." );
         }
 
         final File destDirectory = getDestFile();

src/main/java/org/codehaus/plexus/archiver/exceptions/EmptyArchiveException.java

@@ -0,0 +1,34 @@
+/**
+ * Copyright 2004 The Apache Software Foundation
+ * <p/>
+ * 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
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * 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 org.codehaus.plexus.archiver.exceptions;
+
+import org.codehaus.plexus.archiver.ArchiverException;
+
+public class EmptyArchiveException
+    extends ArchiverException
+{
+
+    public EmptyArchiveException(String message )
+    {
+        super( message );
+    }
+
+    public EmptyArchiveException(String message, Throwable cause )
+    {
+        super( message, cause );
+    }
+
+}

src/main/java/org/codehaus/plexus/archiver/tar/TarArchiver.java

@@ -30,6 +30,7 @@
 import org.codehaus.plexus.archiver.ArchiveEntry;
 import org.codehaus.plexus.archiver.ArchiverException;
 import org.codehaus.plexus.archiver.ResourceIterator;
+import org.codehaus.plexus.archiver.exceptions.EmptyArchiveException;
 import org.codehaus.plexus.archiver.util.ResourceUtils;
 import org.codehaus.plexus.archiver.util.Streams;
 import org.codehaus.plexus.components.io.attributes.PlexusIoResourceAttributes;
@@ -110,7 +111,7 @@ protected void execute()
         ResourceIterator iter = getResources();
         if ( !iter.hasNext() )
         {
-            throw new ArchiverException( "You must set at least one file." );
+            throw new EmptyArchiveException( "You must set at least one file." );
         }
 
         File tarFile = getDestFile();

src/main/java/org/codehaus/plexus/archiver/zip/AbstractZipArchiver.java

@@ -40,6 +40,7 @@
 import org.codehaus.plexus.archiver.ArchiverException;
 import org.codehaus.plexus.archiver.ResourceIterator;
 import org.codehaus.plexus.archiver.UnixStat;
+import org.codehaus.plexus.archiver.exceptions.EmptyArchiveException;
 import org.codehaus.plexus.archiver.util.ResourceUtils;
 import org.codehaus.plexus.components.io.functions.SymlinkDestinationSupplier;
 import org.codehaus.plexus.components.io.resources.PlexusIoResource;
@@ -254,7 +255,7 @@ private void createArchiveMain()
         ResourceIterator iter = getResources();
         if ( !iter.hasNext() && !hasVirtualFiles() )
         {
-            throw new ArchiverException( "You must set at least one file." );
+            throw new EmptyArchiveException( "You must set at least one file." );
         }
 
         zipFile = getDestFile();