Fix tag sorting in PlotWalk

By deferring tag sorting until the commit is produced by the walker
we can avoid an infinite loop that was triggered by trying to sort
tags while allocating a commit.  This also avoids needing to look
at commits which aren't going to be produced in the result.

Bug: 321103
Change-Id: I25acc739db2ec0221a50b72c2d2aa618a9a75f37
Reviewed-by: Mathias Kinzler <mathias.kinzler@sap.com>
Reviewed-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

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

@@ -65,19 +65,16 @@ public class PlotCommit<L extends PlotLane> extends RevCommit {
 
 	PlotCommit[] children;
 
-	final Ref[] refs;
+	Ref[] refs;
 
 	/**
 	 * Create a new commit.
 	 *
 	 * @param id
 	 *            the identity of this commit.
-	 * @param tags
-	 *            the tags associated with this commit, null for no tags
 	 */
-	protected PlotCommit(final AnyObjectId id, final Ref[] tags) {
+	protected PlotCommit(final AnyObjectId id) {
 		super(id);
-		this.refs = tags;
 		passingLanes = NO_LANES;
 		children = NO_CHILDREN;
 	}

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

@@ -45,12 +45,15 @@
 package org.eclipse.jgit.revplot;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.Map;
 import java.util.Set;
 
 import org.eclipse.jgit.JGitText;
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.lib.Ref;
@@ -93,23 +96,26 @@ public class PlotWalk extends RevWalk {
 
 	@Override
 	protected RevCommit createCommit(final AnyObjectId id) {
-		return new PlotCommit(id, getTags(id));
+		return new PlotCommit(id);
 	}
 
-	/**
-	 * @param commitId
-	 * @return return the list of knows tags referring to this commit
-	 */
-	protected Ref[] getTags(final AnyObjectId commitId) {
+	@Override
+	public RevCommit next() throws MissingObjectException,
+			IncorrectObjectTypeException, IOException {
+		PlotCommit<?> pc = (PlotCommit) super.next();
+		if (pc != null)
+			pc.refs = getTags(pc);
+		return pc;
+	}
+
+	private Ref[] getTags(final AnyObjectId commitId) {
 		Collection<Ref> list = reverseRefMap.get(commitId);
 		Ref[] tags;
 		if (list == null)
 			tags = null;
 		else {
 			tags = list.toArray(new Ref[list.size()]);
-			// TODO hotfix, this results in a loop and consequently stack overflow
-			// when opening the history view in EGit
-			// Arrays.sort(tags, new PlotRefComparator());
+			Arrays.sort(tags, new PlotRefComparator());
 		}
 		return tags;
 	}