Merge "Fix resource leak in DiffFormatter"

org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java

@@ -173,7 +173,7 @@ public class DiffFormatter implements AutoCloseable {
 	 */
 	public void setRepository(Repository repository) {
 		if (reader != null)
-			reader.release();
+			reader.close();
 
 		db = repository;
 		reader = db.newObjectReader();
@@ -422,11 +422,12 @@ public class DiffFormatter implements AutoCloseable {
 			throws IOException {
 		assertHaveRepository();
 
-		RevWalk rw = new RevWalk(reader);
+		try (RevWalk rw = new RevWalk(reader)) {
 			RevTree aTree = a != null ? rw.parseTree(a) : null;
 			RevTree bTree = b != null ? rw.parseTree(b) : null;
 			return scan(aTree, bTree);
 		}
+	}
 
 	/**
 	 * Determine the differences between two trees.