Add debugging toString to TreeFormatter

Displaying the current tree in the ls-tree style output makes it
easier to see what entries are currently stored.

Change-Id: If17c414db0d2e8d84e65de8bbcba7fd1b79aa311
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Reviewed-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/lib/TreeFormatter.java

@@ -52,9 +52,11 @@ import static org.eclipse.jgit.lib.FileMode.TREE;
 
 import java.io.IOException;
 
+import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevTree;
+import org.eclipse.jgit.treewalk.CanonicalTreeParser;
 import org.eclipse.jgit.util.TemporaryBuffer;
 
 /**
@@ -311,4 +313,38 @@ public class TreeFormatter {
 			throw new RuntimeException(err);
 		}
 	}
+
+	@Override
+	public String toString() {
+		byte[] raw = toByteArray();
+
+		CanonicalTreeParser p = new CanonicalTreeParser();
+		p.reset(raw);
+
+		StringBuilder r = new StringBuilder();
+		r.append("Tree={");
+		if (!p.eof()) {
+			r.append('\n');
+			try {
+				new ObjectChecker().checkTree(raw);
+			} catch (CorruptObjectException error) {
+				r.append("*** ERROR: ").append(error.getMessage()).append("\n");
+				r.append('\n');
+			}
+		}
+		while (!p.eof()) {
+			final FileMode mode = p.getEntryFileMode();
+			r.append(mode);
+			r.append(' ');
+			r.append(Constants.typeString(mode.getObjectType()));
+			r.append(' ');
+			r.append(p.getEntryObjectId().name());
+			r.append(' ');
+			r.append(p.getEntryPathString());
+			r.append('\n');
+			p.next();
+		}
+		r.append("}");
+		return r.toString();
+	}
 }