Index: AbstractMergeSet.java
===================================================================
--- AbstractMergeSet.java	(revision 0)
+++ AbstractMergeSet.java	(revision 0)
@@ -0,0 +1,93 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.w3c.dom.Element;
+
+/**
+ * Abstract class containing a set of items that need to be merged, split up into items
+ * that just appear in the left-hand side, those in the right-hand side, and
+ * those that are in both (potential conflicts).
+ * 
+ * @version $Id $
+ *
+ */
+public abstract class AbstractMergeSet
+{
+    /**
+     * Items just in the left hand side 
+     */
+    public List inLeftOnly = new ArrayList();
+
+    /**
+     * Items just in the right hand side
+     */
+    public List inRightOnly = new ArrayList();
+
+    /**
+     * Items in both sides (conflicts)
+     */
+    public List inBoth = new ArrayList();
+
+    /**
+     * Perform the merge using the passed strategy
+     * @param action in the strategy to use when merging
+     * @return the count of merges performed
+     */
+    public int merge(MergeStrategy action)
+    {
+        int count = 0;
+
+        for (Iterator i = this.inLeftOnly.iterator(); i.hasNext();)
+        {
+            Element element = (Element) i.next();
+            count += action.inLeft(this, element);
+        }
+        for (Iterator i = this.inRightOnly.iterator(); i.hasNext();)
+        {
+            Element element = (Element) i.next();
+            count += action.inRight(this, element);
+        }
+        // Merge common items by overwriting them
+        for (Iterator i = this.inBoth.iterator(); i.hasNext();)
+        {
+            MergePair pair = (MergePair) i.next();
+            count += action.inBoth(this, pair);
+        }
+        return count;
+    }
+
+    /**
+     * As a result of the merge, add an element to the output
+     * @param e the element to be added
+     */
+    public abstract void add(Element e);
+
+    /**
+     * As a result of the merge, remove an element from the output
+     * @param e the element to be removed
+     */
+    public abstract void remove(Element e);
+
+}
Index: MergeProcessor.java
===================================================================
--- MergeProcessor.java	(revision 0)
+++ MergeProcessor.java	(revision 0)
@@ -0,0 +1,43 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+
+/**
+ * Interface implemented by merger classes. 
+ * @version $Id $
+ *
+ */
+public interface MergeProcessor
+{    
+    /**
+     * Add an item to be merged 
+     * @param mergeItem in the item to merge.
+     * @throws MergeException on exceptions
+     */
+    void addMergeItem(Object mergeItem) throws MergeException;
+    
+    /**
+     * Perform the merge
+     * @return the merged artifact
+     * @throws MergeException if there is a problem 
+     */
+    Object performMerge() throws MergeException;    
+}
Index: MergeNodeList.java
===================================================================
--- MergeNodeList.java	(revision 0)
+++ MergeNodeList.java	(revision 0)
@@ -0,0 +1,116 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import java.util.Iterator;
+
+import org.codehaus.cargo.util.xml.AbstractElement;
+import org.codehaus.cargo.util.xml.AbstractNodeList;
+import org.w3c.dom.Element;
+
+/**
+ * A MergedNodeList is a MergeSet that applies to AbstractNodeLists
+ *
+ * @version $Id $
+ */
+public class MergeNodeList extends AbstractMergeSet
+{
+    /**
+     * The set of everything from the left hand side 
+     */
+    private AbstractNodeList leftSet;
+
+    /**
+     * The set of everything from the right hand side
+     */
+    private AbstractNodeList rightSet;
+
+    /**
+     * Constructor
+     * @param leftSet in the left hand set
+     * @param rightSet in the right hand set
+     */
+    protected MergeNodeList(AbstractNodeList leftSet, AbstractNodeList rightSet)
+    {
+        this.leftSet = leftSet;
+        this.rightSet = rightSet;
+    }
+
+    /**
+     * Static constructor. Make a merge set from the two node sets, using the
+     * elements 'name' in order to determine whether it is in conflict
+     * 
+     * @param leftSet in the left hand set
+     * @param rightSet in the right hand set
+     * @return the generated merge set
+     */
+    public static final AbstractMergeSet createFromNames(AbstractNodeList leftSet,
+        AbstractNodeList rightSet)
+    {
+        AbstractMergeSet results = new MergeNodeList(leftSet, rightSet);
+
+        Iterator i = leftSet.iterator();
+        while (i.hasNext())
+        {
+            AbstractElement left = (AbstractElement) i.next();
+            AbstractElement right = rightSet.getByElementId(left.getElementId());
+
+            if (right == null)
+            {
+                results.inLeftOnly.add(left);
+            }
+            else
+            {
+                results.inBoth.add(new MergePair(left, right));
+            }
+        }
+
+        i = rightSet.iterator();
+
+        while (i.hasNext())
+        {
+            AbstractElement right = (AbstractElement) i.next();
+            AbstractElement left = leftSet.getByElementId(right.getElementId());
+
+            if (left == null)
+            {
+                results.inRightOnly.add(right);
+            }
+        }
+        return results;
+    }
+
+    
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#add(org.w3c.dom.Element)
+     */
+    public void add(Element e)
+    {
+        this.leftSet.add(e);       
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#remove(org.w3c.dom.Element)
+     */
+    public void remove(Element e)
+    {
+        this.leftSet.remove(e);        
+    }
+}
Index: MergeStrategy.java
===================================================================
--- MergeStrategy.java	(revision 0)
+++ MergeStrategy.java	(revision 0)
@@ -0,0 +1,99 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+
+/**
+ * A merge strategy is a vistor/stratey defining some way in which potential 
+ * merge conflicts can be resolved in the set.
+ * 
+ * @version $Id $
+ *
+ */
+public class MergeStrategy
+{
+    /**
+     * Preserve strategy only adds items from the right
+     */
+    public static final MergeStrategy PRESERVE = new MergeStrategy()
+    {
+        public int inRight(AbstractMergeSet set, Element element)
+        {
+            set.add(element);
+            return 1;
+        }
+    };
+
+    /**
+     * Overwrite strategy adds items from the right, and overwrites
+     * duplicates.
+     */
+    public static final MergeStrategy OVERWRITE = new MergeStrategy()
+    {
+        public int inRight(AbstractMergeSet set, Element element)
+        {
+            set.add(element);
+            return 1;
+        }
+
+        int inBoth(AbstractMergeSet set, MergePair pair)
+        {
+            // Merge common items by overwriting them
+            set.remove(pair.left);
+            set.add(pair.right);
+            return 1;
+        }
+    };
+
+    /**
+     * Deal with merging an element that only appears in the left set 
+     * @param set in the calling MergeSet
+     * @param element in the item present only in the left set
+     * @return count of merged items
+     */
+    int inLeft(AbstractMergeSet set, Element element)
+    {
+        return 0;
+    }
+
+    /**
+     * Deal with merging an element that only appears in the right set 
+     * @param set in the calling MergeSet
+     * @param element in the item present only in the left set
+     * @return count of merged items
+     */
+    int inRight(AbstractMergeSet set, Element element)
+    {
+        return 0;
+    }
+
+    /**
+     * Deal with merging an element appears in both sets 
+     * @param set in the calling MergeSet
+     * @param pair the pair of items
+     * @return count of merged items
+     */
+    int inBoth(AbstractMergeSet set, MergePair pair)
+    {
+        return 0;
+    }
+
+}
Index: MergeElement.java
===================================================================
--- MergeElement.java	(revision 0)
+++ MergeElement.java	(revision 0)
@@ -0,0 +1,85 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+
+/**
+ * MergeElement - a MergeSet that only contains one element from left or right
+ *
+ * @version $Id $
+ */
+public class MergeElement extends AbstractMergeSet
+{
+    /**
+     * The parent of the left-hand element
+     */
+    private Element leftParent;
+
+    /**
+     * Constructor.
+     * 
+     * NB: leftParent is needed as it is allowable for left to be null, in 
+     * the event that it does not exist (And so could not be determined otherwise)
+     * 
+     * @param leftParent in the left hand elements parent
+     * @param left in the left hand element
+     * @param right in the right hand element
+     */
+    public MergeElement(Element leftParent, Element left, Element right)
+    {
+        super();
+
+        this.leftParent = leftParent;
+
+        if (left == null)
+        {
+            this.inRightOnly.add(right);
+        }
+        else if (right == null)
+        {
+            this.inLeftOnly.add(left);
+        }
+        else
+        {
+            this.inBoth.add(new MergePair(left, right));
+        }
+
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#add(org.w3c.dom.Element)
+     */
+    public void add(Element e)
+    {
+        Node n = this.leftParent.getOwnerDocument().importNode(e, true);
+        this.leftParent.appendChild(n);
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#remove(org.w3c.dom.Element)
+     */
+    public void remove(Element e)
+    {
+        this.leftParent.removeChild(e);
+    }
+
+}
Index: MergePair.java
===================================================================
--- MergePair.java	(revision 0)
+++ MergePair.java	(revision 0)
@@ -0,0 +1,52 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+
+/**
+ * Class containing a pair of items that need to be merged.
+ * 
+ * @version $Id $
+ *
+ */
+public class MergePair
+{
+    /**
+     * Left and right hand elements 
+     */
+    public Element left;
+    
+    /**
+     * right 
+     */
+    public Element right;
+
+    /**
+     * Constructor
+     * @param left left element
+     * @param right right element
+     */
+    MergePair(Element left, Element right)
+    {
+        this.left = left;
+        this.right = right;
+    }
+}
Index: MergeException.java
===================================================================
--- MergeException.java	(revision 0)
+++ MergeException.java	(revision 0)
@@ -0,0 +1,54 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+/**
+ * Class for various exceptions happening within merges
+ * 
+ * @version $Id $
+ */
+public class MergeException extends Exception
+{
+    /**
+     * Constructor
+     * @param e in cause of the exception
+     */
+    public MergeException(Throwable e)
+    {
+        super(e);
+    }
+
+    /**
+     * @param string in string to describe the exception
+     */
+    public MergeException(String string)
+    {
+        super(string);
+    }
+
+    /**
+     * @param string in string to describe the exception
+     * @param e in causing exception
+     */
+    public MergeException(String string, Exception e)
+    {
+        super(string, e);
+    }
+}
Index: AbstractMergeSet.java
===================================================================
--- AbstractMergeSet.java	(revision 0)
+++ AbstractMergeSet.java	(revision 0)
@@ -0,0 +1,93 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.w3c.dom.Element;
+
+/**
+ * Abstract class containing a set of items that need to be merged, split up into items
+ * that just appear in the left-hand side, those in the right-hand side, and
+ * those that are in both (potential conflicts).
+ * 
+ * @version $Id $
+ *
+ */
+public abstract class AbstractMergeSet
+{
+    /**
+     * Items just in the left hand side 
+     */
+    public List inLeftOnly = new ArrayList();
+
+    /**
+     * Items just in the right hand side
+     */
+    public List inRightOnly = new ArrayList();
+
+    /**
+     * Items in both sides (conflicts)
+     */
+    public List inBoth = new ArrayList();
+
+    /**
+     * Perform the merge using the passed strategy
+     * @param action in the strategy to use when merging
+     * @return the count of merges performed
+     */
+    public int merge(MergeStrategy action)
+    {
+        int count = 0;
+
+        for (Iterator i = this.inLeftOnly.iterator(); i.hasNext();)
+        {
+            Element element = (Element) i.next();
+            count += action.inLeft(this, element);
+        }
+        for (Iterator i = this.inRightOnly.iterator(); i.hasNext();)
+        {
+            Element element = (Element) i.next();
+            count += action.inRight(this, element);
+        }
+        // Merge common items by overwriting them
+        for (Iterator i = this.inBoth.iterator(); i.hasNext();)
+        {
+            MergePair pair = (MergePair) i.next();
+            count += action.inBoth(this, pair);
+        }
+        return count;
+    }
+
+    /**
+     * As a result of the merge, add an element to the output
+     * @param e the element to be added
+     */
+    public abstract void add(Element e);
+
+    /**
+     * As a result of the merge, remove an element from the output
+     * @param e the element to be removed
+     */
+    public abstract void remove(Element e);
+
+}
Index: MergeElement.java
===================================================================
--- MergeElement.java	(revision 0)
+++ MergeElement.java	(revision 0)
@@ -0,0 +1,85 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+
+/**
+ * MergeElement - a MergeSet that only contains one element from left or right
+ *
+ * @version $Id $
+ */
+public class MergeElement extends AbstractMergeSet
+{
+    /**
+     * The parent of the left-hand element
+     */
+    private Element leftParent;
+
+    /**
+     * Constructor.
+     * 
+     * NB: leftParent is needed as it is allowable for left to be null, in 
+     * the event that it does not exist (And so could not be determined otherwise)
+     * 
+     * @param leftParent in the left hand elements parent
+     * @param left in the left hand element
+     * @param right in the right hand element
+     */
+    public MergeElement(Element leftParent, Element left, Element right)
+    {
+        super();
+
+        this.leftParent = leftParent;
+
+        if (left == null)
+        {
+            this.inRightOnly.add(right);
+        }
+        else if (right == null)
+        {
+            this.inLeftOnly.add(left);
+        }
+        else
+        {
+            this.inBoth.add(new MergePair(left, right));
+        }
+
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#add(org.w3c.dom.Element)
+     */
+    public void add(Element e)
+    {
+        Node n = this.leftParent.getOwnerDocument().importNode(e, true);
+        this.leftParent.appendChild(n);
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#remove(org.w3c.dom.Element)
+     */
+    public void remove(Element e)
+    {
+        this.leftParent.removeChild(e);
+    }
+
+}
Index: MergeException.java
===================================================================
--- MergeException.java	(revision 0)
+++ MergeException.java	(revision 0)
@@ -0,0 +1,54 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+/**
+ * Class for various exceptions happening within merges
+ * 
+ * @version $Id $
+ */
+public class MergeException extends Exception
+{
+    /**
+     * Constructor
+     * @param e in cause of the exception
+     */
+    public MergeException(Throwable e)
+    {
+        super(e);
+    }
+
+    /**
+     * @param string in string to describe the exception
+     */
+    public MergeException(String string)
+    {
+        super(string);
+    }
+
+    /**
+     * @param string in string to describe the exception
+     * @param e in causing exception
+     */
+    public MergeException(String string, Exception e)
+    {
+        super(string, e);
+    }
+}
Index: MergeNodeList.java
===================================================================
--- MergeNodeList.java	(revision 0)
+++ MergeNodeList.java	(revision 0)
@@ -0,0 +1,116 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import java.util.Iterator;
+
+import org.codehaus.cargo.util.xml.AbstractElement;
+import org.codehaus.cargo.util.xml.AbstractNodeList;
+import org.w3c.dom.Element;
+
+/**
+ * A MergedNodeList is a MergeSet that applies to AbstractNodeLists
+ *
+ * @version $Id $
+ */
+public class MergeNodeList extends AbstractMergeSet
+{
+    /**
+     * The set of everything from the left hand side 
+     */
+    private AbstractNodeList leftSet;
+
+    /**
+     * The set of everything from the right hand side
+     */
+    private AbstractNodeList rightSet;
+
+    /**
+     * Constructor
+     * @param leftSet in the left hand set
+     * @param rightSet in the right hand set
+     */
+    protected MergeNodeList(AbstractNodeList leftSet, AbstractNodeList rightSet)
+    {
+        this.leftSet = leftSet;
+        this.rightSet = rightSet;
+    }
+
+    /**
+     * Static constructor. Make a merge set from the two node sets, using the
+     * elements 'name' in order to determine whether it is in conflict
+     * 
+     * @param leftSet in the left hand set
+     * @param rightSet in the right hand set
+     * @return the generated merge set
+     */
+    public static final AbstractMergeSet createFromNames(AbstractNodeList leftSet,
+        AbstractNodeList rightSet)
+    {
+        AbstractMergeSet results = new MergeNodeList(leftSet, rightSet);
+
+        Iterator i = leftSet.iterator();
+        while (i.hasNext())
+        {
+            AbstractElement left = (AbstractElement) i.next();
+            AbstractElement right = rightSet.getByElementId(left.getElementId());
+
+            if (right == null)
+            {
+                results.inLeftOnly.add(left);
+            }
+            else
+            {
+                results.inBoth.add(new MergePair(left, right));
+            }
+        }
+
+        i = rightSet.iterator();
+
+        while (i.hasNext())
+        {
+            AbstractElement right = (AbstractElement) i.next();
+            AbstractElement left = leftSet.getByElementId(right.getElementId());
+
+            if (left == null)
+            {
+                results.inRightOnly.add(right);
+            }
+        }
+        return results;
+    }
+
+    
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#add(org.w3c.dom.Element)
+     */
+    public void add(Element e)
+    {
+        this.leftSet.add(e);       
+    }
+
+    /**
+     * @see org.codehaus.cargo.module.merge.AbstractMergeSet#remove(org.w3c.dom.Element)
+     */
+    public void remove(Element e)
+    {
+        this.leftSet.remove(e);        
+    }
+}
Index: MergePair.java
===================================================================
--- MergePair.java	(revision 0)
+++ MergePair.java	(revision 0)
@@ -0,0 +1,52 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+
+/**
+ * Class containing a pair of items that need to be merged.
+ * 
+ * @version $Id $
+ *
+ */
+public class MergePair
+{
+    /**
+     * Left and right hand elements 
+     */
+    public Element left;
+    
+    /**
+     * right 
+     */
+    public Element right;
+
+    /**
+     * Constructor
+     * @param left left element
+     * @param right right element
+     */
+    MergePair(Element left, Element right)
+    {
+        this.left = left;
+        this.right = right;
+    }
+}
Index: MergeProcessor.java
===================================================================
--- MergeProcessor.java	(revision 0)
+++ MergeProcessor.java	(revision 0)
@@ -0,0 +1,43 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+
+/**
+ * Interface implemented by merger classes. 
+ * @version $Id $
+ *
+ */
+public interface MergeProcessor
+{    
+    /**
+     * Add an item to be merged 
+     * @param mergeItem in the item to merge.
+     * @throws MergeException on exceptions
+     */
+    void addMergeItem(Object mergeItem) throws MergeException;
+    
+    /**
+     * Perform the merge
+     * @return the merged artifact
+     * @throws MergeException if there is a problem 
+     */
+    Object performMerge() throws MergeException;    
+}
Index: MergeStrategy.java
===================================================================
--- MergeStrategy.java	(revision 0)
+++ MergeStrategy.java	(revision 0)
@@ -0,0 +1,99 @@
+/* 
+ * ========================================================================
+ * 
+ * Copyright 2004-2005 Vincent Massol.
+ *
+ * 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
+ * 
+ *   http://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 org.codehaus.cargo.module.merge;
+
+import org.w3c.dom.Element;
+
+/**
+ * A merge strategy is a vistor/stratey defining some way in which potential 
+ * merge conflicts can be resolved in the set.
+ * 
+ * @version $Id $
+ *
+ */
+public class MergeStrategy
+{
+    /**
+     * Preserve strategy only adds items from the right
+     */
+    public static final MergeStrategy PRESERVE = new MergeStrategy()
+    {
+        public int inRight(AbstractMergeSet set, Element element)
+        {
+            set.add(element);
+            return 1;
+        }
+    };
+
+    /**
+     * Overwrite strategy adds items from the right, and overwrites
+     * duplicates.
+     */
+    public static final MergeStrategy OVERWRITE = new MergeStrategy()
+    {
+        public int inRight(AbstractMergeSet set, Element element)
+        {
+            set.add(element);
+            return 1;
+        }
+
+        int inBoth(AbstractMergeSet set, MergePair pair)
+        {
+            // Merge common items by overwriting them
+            set.remove(pair.left);
+            set.add(pair.right);
+            return 1;
+        }
+    };
+
+    /**
+     * Deal with merging an element that only appears in the left set 
+     * @param set in the calling MergeSet
+     * @param element in the item present only in the left set
+     * @return count of merged items
+     */
+    int inLeft(AbstractMergeSet set, Element element)
+    {
+        return 0;
+    }
+
+    /**
+     * Deal with merging an element that only appears in the right set 
+     * @param set in the calling MergeSet
+     * @param element in the item present only in the left set
+     * @return count of merged items
+     */
+    int inRight(AbstractMergeSet set, Element element)
+    {
+        return 0;
+    }
+
+    /**
+     * Deal with merging an element appears in both sets 
+     * @param set in the calling MergeSet
+     * @param pair the pair of items
+     * @return count of merged items
+     */
+    int inBoth(AbstractMergeSet set, MergePair pair)
+    {
+        return 0;
+    }
+
+}