Add Instructions on how to build FRLG by default (#9415)

docs/tutorials/how_to_frlg.md

@@ -44,3 +44,125 @@ Porymap:
 ## Migrating FRLG tilesets
 To migrate tilesets that have been previously created for pokefirered you can use [this script](/migration_scripts/frlg_metatile_behavior_converter.py).<br>
 Instructions are in the script.
+
+## Disclaimer: The changes below aren't the permanent solution for the problems, A better build system is being worked on so these solutions might cause merge conflicts down the line
+
+## Build FRLG by default
+If you want that running `make -j<output of nproc>` to directly compile one of firered or leafgreen instead of emerald make the following changes to the `makefile`
+
+(Here I have set the default version to be leafgreen and you can still compile emerald or firered using make emerald or make firered)
+
+```diff
+-GAME_VERSION ?= EMERALD
+-TITLE        ?= POKEMON EMER
+-GAME_CODE    ?= BPEE
+-BUILD_NAME   ?= emerald
+-MAP_VERSION  ?= emerald
++GAME_VERSION ?= LEAFGREEN
++TITLE        ?= POKEMON LEAF
++GAME_CODE    ?= BPGE
++BUILD_NAME   ?= leafgreen
++MAP_VERSION  ?= firered
+
+ifeq (firered,$(MAKECMDGOALS))
+  	GAME_VERSION 	:= FIRERED
+	TITLE       	:= POKEMON FIRE
+	GAME_CODE   	:= BPRE
+	BUILD_NAME  	:= firered
+	MAP_VERSION 	:= firered
+else
+
+-ifeq (leafgreen,$(MAKECMDGOALS))
+-	GAME_VERSION 	:= LEAFGREEN
+-	TITLE       	:= POKEMON LEAF
+-	GAME_CODE   	:= BPGE
+-	BUILD_NAME  	:= leafgreen
+-	MAP_VERSION 	:= firered
++ifeq (emerald,$(MAKECMDGOALS))
++	GAME_VERSION 	:= EMERALD
++	TITLE       	:= POKEMON EMER
++	GAME_CODE   	:= BPEE
++	BUILD_NAME  	:= emerald
++	MAP_VERSION 	:= emerald
+endif
+endif
+```
+
+## Make empty region attibutes defaults to REGION_KANTO
+Another issue is that you need to add `REGION_KANTO` attribute to every new map you create
+
+Make the following changes to your `tools/mapjson/mapjson.cpp` so the new maps you add without the `REGION_KANTO` also work fine
+
+```diff
+string region = json_to_string(map_data, "region", true);
+
+        if (region.empty()) {
+-            region = "REGION_HOENN";
++            region = "REGION_KANTO";
+        }
+        string map_name = json_to_string(map_data, "name");
+
+        if ((version == "emerald" && region != "REGION_HOENN")
+         || (version == "firered" && region != "REGION_KANTO")) {
+            invalid_maps.push_back(map_name);
+        }
+```
+
+Then run this script to set `REGION_KANTO` as the region attribute for all the Hoenn Maps
+
+**Make sure you run this from the [root folder](../../) of your project!**
+
+```
+python3 migration_scripts/add_region_hoenn_attribute_to_hoenn_maps.py
+```
+
+Make sure to run `make clean` after running this script
+
+## Fix CI if you are building FRLG by default
+If you make these I would also reccomend fixing your CI too to match these changes
+
+Make the following changes to your `.github/workflows/build.yml`
+
+```diff
+# build-essential and git are already installed
+
+-      - name: ROM (Emerald)
++      - name: ROM (Leafgreen)
+        env:
+          COMPARE: 0
+-          GAME_VERSION: EMERALD
++          GAME_VERSION: LEAFGREEN
+        run: make -j${nproc} -O all
+
+      - name: Release
+        env:
+-          GAME_VERSION: EMERALD
++          GAME_VERSION: LEAFGREEN
+        run: |
+          make tidy
+          make -j${nproc} release
+        # make tidy to purge previous build
+
+      - name: Test
+        env:
+-          GAME_VERSION: EMERALD
++          GAME_VERSION: LEAFGREEN
+          TEST: 1
+        run: |
+          make -j${nproc} check
+
+      - name: ROM (Firered)
+        env:
+          COMPARE: 0
+        run: |
+          make clean
+          make firered -j${nproc} -O
+
+-      - name: ROM (Leafgreen)
++      - name: ROM (Emerald)
+        env:
+          COMPARE: 0
+        run: |
+-          make leafgreen -j${nproc} -O
++          make emerald -j${nproc} -O
+```

migration_scripts/add_region_hoenn_attribute_to_hoenn_maps.py

@@ -0,0 +1,42 @@
+import os
+
+MAPS_DIR = "/data/maps"
+
+for root, dirs, files in os.walk(MAPS_DIR):
+    for file in files:
+        if not file.endswith(".json"):
+            continue
+
+        if file.endswith("_Frlg.json"):
+            continue
+
+        filepath = os.path.join(root, file)
+
+        with open(filepath, "r", encoding="utf-8") as f:
+            lines = f.readlines()
+
+        # Skip if region already exists
+        if any('"region"' in line for line in lines):
+            continue
+
+        new_lines = []
+        inserted = False
+
+        for i, line in enumerate(lines):
+            new_lines.append(line)
+
+            if '"music"' in line and not inserted:
+                # Detect indentation from current line
+                indent = line[:len(line) - len(line.lstrip())]
+
+                region_line = f'{indent}"region": "REGION_HOENN",\n'
+                new_lines.append(region_line)
+                inserted = True
+
+        if inserted:
+            with open(filepath, "w", encoding="utf-8") as f:
+                f.writelines(new_lines)
+
+            print(f"Updated: {filepath}")
+
+print("Done.")