Make it possible to clear a PlotCommitList

This allows SwingGraphPanes to be reused by simply clearing and
re-filling. Requires RevObjectList initialization to not call clear()
from its constructor, because this will lead PlotCommitList.clear()
to be called before all variables have been initialized.

Change-Id: I14a07124441b58cd88c67da088ba52ef9c30b043
Signed-off-by: Jonas Fonseca <fonseca@diku.dk>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java

@@ -70,7 +70,15 @@ public class PlotCommitList<L extends PlotLane> extends
 
 	private final TreeSet<Integer> freeLanes = new TreeSet<Integer>();
 
-	private HashSet<PlotLane> activeLanes = new HashSet<PlotLane>(32);
+	private final HashSet<PlotLane> activeLanes = new HashSet<PlotLane>(32);
+
+	@Override
+	public void clear() {
+		super.clear();
+		lanesAllocated = 0;
+		freeLanes.clear();
+		activeLanes.clear();
+	}
 
 	@Override
 	public void source(final RevWalk w) {
@@ -139,7 +147,7 @@ public class PlotCommitList<L extends PlotLane> extends
 				final PlotCommit c = currCommit.children[i];
 				if (activeLanes.remove(c.lane)) {
 					recycleLane((L) c.lane);
-					freeLanes.add(Integer.valueOf(c.lane.position));
+					freeLanes.add(Integer.valueOf(c.lane.getPosition()));
 				}
 			}
 

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevObjectList.java

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2009, Jonas Fonseca <fonseca@diku.dk>
  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
  * and other copyright owners as documented in the project's IP log.
  *
@@ -56,13 +57,12 @@ public class RevObjectList<E extends RevObject> extends AbstractList<E> {
 
 	static final int BLOCK_SIZE = 1 << BLOCK_SHIFT;
 
-	Block contents;
+	protected Block contents = new Block(0);
 
-	int size;
+	protected int size = 0;
 
 	/** Create an empty object list. */
 	public RevObjectList() {
-		clear();
 	}
 
 	public void add(final int index, final E element) {
@@ -113,7 +113,7 @@ public class RevObjectList<E extends RevObject> extends AbstractList<E> {
 		size = 0;
 	}
 
-	static class Block {
+	protected static class Block {
 		final Object[] contents = new Object[BLOCK_SIZE];
 
 		final int shift;