Merging Rollup2 fixes into branch R1_0

bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/dtree/DeltaDataTree.java

diff --git a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/dtree/DeltaDataTree.java b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/dtree/DeltaDataTree.java
index 3a03354..cff6d11 100644
--- a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/dtree/DeltaDataTree.java
+++ b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/dtree/DeltaDataTree.java
@@ -205,6 +205,33 @@
 	return newTree;

 }

 /**

+ * Collapses this tree so that the given ancestor becomes its

+ * immediate parent.  Afterwards, this tree will still have exactly the

+ * same contents, but its internal stucture will be compressed.

+ *

+ * <p> This operation should be used to collapse chains of

+ * delta trees that don't contain interesting intermediate states.

+ *

+ * <p>This is a destructive operation, since it modifies the structure of this 

+ * tree instance.  This tree must be immutable at the start of this operation,

+ * and will be immutable afterwards.  

+ * @return this tree.

+ */

+public DeltaDataTree collapseTo(DeltaDataTree parent, IComparator comparator) {

+	if (this == parent || getParent() == parent) {

+		//already collapsed

+		return this;

+	}

+	//collapse my tree to be a forward delta of the parent's tree.

+	//c will have the same content as this tree, but its parent will be "parent".

+	DeltaDataTree c = parent.forwardDeltaWith(this, comparator);

+

+	//update my internal root node and parent pointers.

+	this.parent = parent;

+	this.rootNode = c.rootNode;

+	return this;

+}

+/**

  * Returns a DeltaDataTree that describes the differences between

  * this tree and "other" tree.  Each node of the returned tree

  * will contain a NodeComparison object that describes the differences

bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java

diff --git a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java
index b231d4c..884244e 100644
--- a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java
+++ b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/watson/ElementTree.java
@@ -177,15 +177,12 @@
  */

 public ElementTree collapseTo(ElementTree parent) {

 	Assert.isTrue(tree.isImmutable());

-	if (this == parent || getParent() == parent) {

+	if (this == parent) {

 		//already collapsed

 		return this;

 	}

 	//collapse my tree to be a forward delta of the parent's tree.

-	DeltaDataTree c = parent.tree.forwardDeltaWith(tree, DefaultElementComparator.getComparator());

-

-	//update my internal tree

-	this.tree = c;

+	tree.collapseTo(parent.tree, DefaultElementComparator.getComparator());

 	return this;

 }

 /**