Update Lab 1 instructions (Java 11 and Lab 2)

lab1.md

@@ -57,15 +57,33 @@ fixes, new commits to the HW repo, etc., as bugs and issues are reported.
 following the instructions
 [here](https://github.com/MIT-DB-Class/simple-db-hw-2022).**
 
+------
+
+**Update (09/26/2022):** If you are starting this lab on or after September 26,
+the code that you will get from this repository will include the starter code
+and the tests for later labs. To get only the subset of the code and tests used
+for lab 1, switch to the `lab1` branch (`git checkout lab1`).
+
+------
+
 These instructions are written for Athena or any other Unix-based platform
 (e.g., Linux, macOS, etc.)  Because the code is written in Java, it should work
 under Windows as well, although the directions in this document may not apply.
 
 Unless you are running on Athena, you will also need to make sure you have a
 Java Development Kit (JDK) installed. SimpleDB requires at least Java 8 (note
 that "Java 8" and "Java 1.8" refer to the same version of Java—the former is
-used for branding purposes). **Our autograder uses Java 11, so please do not use
-any features newer than Java 11 (you will not need them for the lab).**
+used for branding purposes). This project has been configured to use Java 11 by
+default. If you are running an older version of Java, you will need to update
+following line in `build.xml`:
+
+```xml
+<!-- Update the value below to match your version (e.g., "1.8"). -->
+<property name="sourceversion" value="11"/>
+```
+
+**Our autograder uses Java 11, so please do not use any features newer than Java
+11 (you will not need them for the lab).**
 
 You can install a JDK as follows:
 - On macOS: `brew install openjdk@11`