Work on documentation for build.py, also add checkout step.

build.py

@@ -1,17 +1,41 @@
 #!/usr/bin/python3
 #
-# This build script can be run in three modes:
+# The one-and-only build script for luprex.
+# Do not follow any of the build instructions on the Unreal Engine
+# websites!  Instead, use these instructions.
 #
-#    build.py all    - rebuilds everything
-#    build.py c++    - works when you've only edited c++ code
-#    build.py clean  - remove some build products
 #
-# If you clone the UnrealEngine and integration repositories,
-# and then run "build.py all", this will build both unreal engine and
-# integration.  It will also build project files for vscode, an
-# intellisense database, and several other things.  Once it is done,
-# you can start up vscode using 'code Integration.code-workspace'.
-# Then, you can run our game in the vscode debugger.
+# HOW TO BUILD THE FIRST TIME
+#
+# First, install the following software:
+#
+#   apt-get install git-lfs
+#   apt-get install code
+#   apt-get install dotnet6
+#   apt-get install clangd-15 or better.
+#
+# Then, git clone the UnrealEngine and integration repositories:
+#
+#   cd $HOME
+#   git clone https://github.com/EpicGames/UnrealEngine.git
+#   git clone https://www.gnaut.com/team/integration.git
+#
+# It is important that these two repositories be located
+# at $HOME/UnrealEngine and $HOME/integration.
+#
+# Of course, you will have to jump through a bunch of hoops to
+# get access to these repositories.  See the instructions on the
+# unreal engine website.
+#
+# After cloning the two repositories, change directory into
+# the "integration" repository and run "build.py all".
+# This will build both unreal engine and integration.  It will
+# also build project files for vscode, an intellisense database,
+# and several other things.  Once it is done, everything is built.
+# You can start up the debugger.
+# 
+# 
+# HOW TO REBUILD WHEN YOU'VE EDITED SOMETHING
 #
 # You can also use "build.py all" to rebuild.  This is the preferred
 # way to rebuild when you aren't sure what's been edited.  However,
@@ -26,12 +50,22 @@
 # anything else, you need to use "build.py all" to rebuild.
 #
 # Editing Lua or Blueprint code doesn't require any kind of rebuild.
+#
+#
+# USING VISUAL STUDIO CODE
 # 
-# We have a "build.py clean", but it hasn't gotten a lot of love.
-# I honestly have no idea what it removes and what it doesn't.
+# To start up vscode, change directory to the integration repository,
+# and run "code Integration.code-workspace".  From inside vscode, you can
+# use Terminal/Run_Build_Task to run "build.py all" or "build.py c++".
+# You can also select Run/Start_Debugging to launch the game.
 #
+# The first time you launch vscode, you will see a popup about
+# recommended extensions.  These are actually recommended by this
+# script, build.py, so they're actually good recommendations.  Install
+# them: you will only have to do this once.
 #
 
+
 import sys, os, json, shutil, subprocess, re, time, tarfile, itertools, hashlib
 from pathlib import Path
 from types import SimpleNamespace
@@ -176,6 +210,13 @@ def store_system_config_in_globals(config):
 # The actual build steps.
 #
 
+def checkout_correct_unreal_engine_branch():
+    """
+    This is the version of Unreal Engine that we're currently using.
+    """
+    shell(UNREALENGINE, "git checkout 5.3.1-release")
+
+
 def generate_buildconfiguration_xml():
     """
     Generates BuildConfiguration.xml.  We actually have two versions of this
@@ -338,6 +379,7 @@ store_system_config_in_globals(CONFIG)
 os.chdir(f"{INTEGRATION}/EnginePatches")
 
 if MODE == "all":
+    checkout_correct_unreal_engine_branch()
     generate_buildconfiguration_xml()
     generate_lpx_paths()
     patch_unrealengine_source_code()