DescribeCommand: Refactor to not use deprecated Repository#peel

Change-Id: I76073ad62d1bc4fc21d8a1f5fc7eb92060a73baa
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/DescribeCommand.java

@@ -224,12 +224,16 @@ public class DescribeCommand extends GitCommand<String> {
 		}
 	}
 
-	private ObjectId getObjectIdFromRef(Ref r) {
-		ObjectId key = repo.peel(r).getPeeledObjectId();
-		if (key == null) {
-			key = r.getObjectId();
+	private ObjectId getObjectIdFromRef(Ref r) throws JGitInternalException {
+		try {
+			ObjectId key = repo.getRefDatabase().peel(r).getPeeledObjectId();
+			if (key == null) {
+				key = r.getObjectId();
+			}
+			return key;
+		} catch (IOException e) {
+			throw new JGitInternalException(e.getMessage(), e);
 		}
-		return key;
 	}
 
 	/**