diff --git a/tools/hooks/install.bat b/tools/hooks/install.bat
new file mode 100644
index 0000000000..c4f864b5c6
--- /dev/null
+++ b/tools/hooks/install.bat
@@ -0,0 +1,14 @@
+@echo off
+cd %~dp0
+for %%f in (*.hook) do (
+	echo Installing hook: %%~nf
+	copy %%f ..\..\.git\hooks\%%~nf >nul
+)
+for %%f in (*.merge) do (
+	echo Installing merge driver: %%~nf
+	echo [merge "%%~nf"]^
+
+	driver = tools/hooks/%%f %%P %%O %%A %%B %%L >> ..\..\.git\config
+)
+echo Done
+pause
diff --git a/tools/hooks/install.sh b/tools/hooks/install.sh
new file mode 100644
index 0000000000..3bcbfe7ff6
--- /dev/null
+++ b/tools/hooks/install.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+cd "$(dirname "$0")"
+for f in *.hook; do
+	echo Installing hook: ${f%.hook}
+	cp $f ../../.git/hooks/${f%.hook}
+done
+for f in *.merge; do
+	echo Installing merge driver: ${f%.merge}
+	git config --replace-all merge.${f%.merge}.driver "tools/hooks/$f %P %O %A %B %L"
+done
+echo "Done"
diff --git a/tools/hooks/pre-commit.hook b/tools/hooks/pre-commit.hook
new file mode 100644
index 0000000000..7eccda6f58
--- /dev/null
+++ b/tools/hooks/pre-commit.hook
@@ -0,0 +1,2 @@
+#!/bin/bash
+exec tools/hooks/python.sh -m precommit
diff --git a/tools/hooks/python.sh b/tools/hooks/python.sh
new file mode 100644
index 0000000000..32557070f4
--- /dev/null
+++ b/tools/hooks/python.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+set -e
+if command -v python3 >/dev/null 2>&1; then
+	PY=python3
+else
+	PY=python
+fi
+PATHSEP=$($PY - <<'EOF'
+import sys, os
+if sys.version_info.major != 3 or sys.version_info.minor < 6:
+	sys.stderr.write("Python 3.6+ is required: " + sys.version + "\n")
+	exit(1)
+print(os.pathsep)
+EOF
+)
+export PYTHONPATH=tools/mapmerge2/${PATHSEP}${PYTHONPATH}
+$PY "$@"
diff --git a/tools/mapmerge2/convert.py b/tools/mapmerge2/convert.py
new file mode 100644
index 0000000000..35e5dda443
--- /dev/null
+++ b/tools/mapmerge2/convert.py
@@ -0,0 +1,8 @@
+#!/usr/bin/env python3
+import frontend
+import dmm
+
+if __name__ == '__main__':
+    settings = frontend.read_settings()
+    for fname in frontend.process(settings, "convert"):
+        dmm.DMM.from_file(fname).to_file(fname, settings.tgm)
diff --git a/tools/mapmerge2/dmm.py b/tools/mapmerge2/dmm.py
new file mode 100644
index 0000000000..155181d413
--- /dev/null
+++ b/tools/mapmerge2/dmm.py
@@ -0,0 +1,459 @@
+# Tools for working with DreamMaker maps
+
+import io
+import bidict
+import random
+from collections import namedtuple
+
+TGM_HEADER = "//MAP CONVERTED BY dmm2tgm.py THIS HEADER COMMENT PREVENTS RECONVERSION, DO NOT REMOVE"
+ENCODING = 'utf-8'
+
+Coordinate = namedtuple('Coordinate', ['x', 'y', 'z'])
+
+class DMM:
+    __slots__ = ['key_length', 'size', 'dictionary', 'grid', 'header']
+
+    def __init__(self, key_length, size):
+        self.key_length = key_length
+        self.size = size
+        self.dictionary = bidict.bidict()
+        self.grid = {}
+        self.header = None
+
+    @staticmethod
+    def from_file(fname):
+        # stream the file rather than forcing all its contents to memory
+        with open(fname, 'r', encoding=ENCODING) as f:
+            return _parse(iter(lambda: f.read(1), ''))
+
+    @staticmethod
+    def from_bytes(bytes):
+        return _parse(bytes.decode(ENCODING))
+
+    def to_file(self, fname, tgm = True):
+        with open(fname, 'w', newline='\n', encoding=ENCODING) as f:
+            (save_tgm if tgm else save_dmm)(self, f)
+
+    def to_bytes(self, tgm = True):
+        bio = io.BytesIO()
+        with io.TextIOWrapper(bio, newline='\n', encoding=ENCODING) as f:
+            (save_tgm if tgm else save_dmm)(self, f)
+            f.flush()
+            return bio.getvalue()
+
+    def generate_new_key(self):
+        # ensure that free keys exist by increasing the key length if necessary
+        free_keys = (BASE ** self.key_length) - len(self.dictionary)
+        while free_keys <= 0:
+            self.key_length += 1
+            free_keys = (BASE ** self.key_length) - len(self.dictionary)
+
+        # choose one of the free keys at random
+        key = 0
+        while free_keys:
+            if key not in self.dictionary:
+                # this construction is used to avoid needing to construct the
+                # full set in order to random.choice() from it
+                if random.random() < 1 / free_keys:
+                    return key
+                free_keys -= 1
+            key += 1
+
+        raise RuntimeError("ran out of keys, this shouldn't happen")
+
+    @property
+    def coords_zyx(self):
+        for z in range(1, self.size.z + 1):
+            for y in range(1, self.size.y + 1):
+                for x in range(1, self.size.x + 1):
+                    yield (z, y, x)
+
+    @property
+    def coords_z(self):
+        return range(1, self.size.z + 1)
+
+    @property
+    def coords_yx(self):
+        for y in range(1, self.size.y + 1):
+            for x in range(1, self.size.x + 1):
+                yield (y, x)
+
+# ----------
+# key handling
+
+# Base 52 a-z A-Z dictionary for fast conversion
+BASE = 52
+base52 = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
+base52_r = {x: i for i, x in enumerate(base52)}
+assert len(base52) == BASE and len(base52_r) == BASE
+
+def key_to_num(key):
+    num = 0
+    for ch in key:
+        num = BASE * num + base52_r[ch]
+    return num
+
+def num_to_key(num, key_length):
+    if num >= BASE ** key_length:
+        raise KeyTooLarge(f"num={num} does not fit in key_length={key_length}")
+
+    result = ''
+    while num:
+        result = base52[num % BASE] + result
+        num //= BASE
+
+    assert len(result) <= key_length
+    return base52[0] * (key_length - len(result)) + result
+
+class KeyTooLarge(Exception):
+    pass
+
+# ----------
+# An actual atom parser
+
+def parse_map_atom(atom):
+    try:
+        i = atom.index('{')
+    except ValueError:
+        return atom, {}
+
+    path, rest = atom[:i], atom[i+1:]
+    vars = {}
+
+    in_string = False
+    in_name = False
+    escaping = False
+    current_name = ''
+    current = ''
+    for ch in rest:
+        if escaping:
+            escaping = False
+            current += ch
+        elif ch == '\\':
+            escaping = True
+        elif ch == '"':
+            in_string = not in_string
+            current += ch
+        elif in_string:
+            current += ch
+        elif ch == ';':
+            vars[current_name.strip()] = current.strip()
+            current_name = current = ''
+        elif ch == '=':
+            current_name = current
+            current = ''
+        elif ch == '}':
+            vars[current_name.strip()] = current.strip()
+            break
+        elif ch not in ' ':
+            current += ch
+
+    return path, vars
+
+# ----------
+# TGM writer
+
+def save_tgm(dmm, output):
+    output.write(f"{TGM_HEADER}\n")
+    if dmm.header:
+        output.write(f"{dmm.header}\n")
+
+    # write dictionary in tgm format
+    for key, value in sorted(dmm.dictionary.items()):
+        output.write(f'"{num_to_key(key, dmm.key_length)}" = (\n')
+        for idx, thing in enumerate(value):
+            in_quote_block = False
+            in_varedit_block = False
+            for char in thing:
+                if in_quote_block:
+                    if char == '"':
+                        in_quote_block = False
+                    output.write(char)
+                elif char == '"':
+                    in_quote_block = True
+                    output.write(char)
+                elif not in_varedit_block:
+                    if char == "{":
+                        in_varedit_block = True
+                        output.write("{\n\t")
+                    else:
+                        output.write(char)
+                elif char == ";":
+                    output.write(";\n\t")
+                elif char == "}":
+                    output.write("\n\t}")
+                    in_varedit_block = False
+                else:
+                    output.write(char)
+            if idx < len(value) - 1:
+                output.write(",\n")
+        output.write(")\n")
+
+    # thanks to YotaXP for finding out about this one
+    max_x, max_y, max_z = dmm.size
+    for z in range(1, max_z + 1):
+        output.write("\n")
+        for x in range(1, max_x + 1):
+            output.write(f"({x},{1},{z}) = {{\"\n")
+            for y in range(1, max_y + 1):
+                output.write(f"{num_to_key(dmm.grid[x, y, z], dmm.key_length)}\n")
+            output.write("\"}\n")
+
+# ----------
+# DMM writer
+
+def save_dmm(dmm, output):
+    if dmm.header:
+        output.write(f"{dmm.header}\n")
+
+    # writes a tile dictionary the same way Dreammaker does
+    for key, value in sorted(dmm.dictionary.items()):
+        output.write(f'"{num_to_key(key, dmm.key_length)}" = ({",".join(value)})\n')
+
+    output.write("\n")
+
+    # writes a map grid the same way Dreammaker does
+    max_x, max_y, max_z = dmm.size
+    for z in range(1, max_z + 1):
+        output.write(f"(1,1,{z}) = {{\"\n")
+
+        for y in range(1, max_y + 1):
+            for x in range(1, max_x + 1):
+                try:
+                    output.write(num_to_key(dmm.grid[x, y, z], dmm.key_length))
+                except KeyError:
+                    print(f"Key error: ({x}, {y}, {z})")
+            output.write("\n")
+        output.write("\"}\n")
+
+# ----------
+# Parser
+
+def _parse(map_raw_text):
+    in_comment_line = False
+    comment_trigger = False
+
+    in_quote_block = False
+    in_key_block = False
+    in_data_block = False
+    in_varedit_block = False
+    after_data_block = False
+    escaping = False
+    skip_whitespace = False
+
+    dictionary = bidict.bidict()
+    duplicate_keys = {}
+    curr_key_len = 0
+    curr_key = 0
+    curr_datum = ""
+    curr_data = list()
+
+    in_map_block = False
+    in_coord_block = False
+    in_map_string = False
+    iter_x = 0
+    adjust_y = True
+
+    curr_num = ""
+    reading_coord = "x"
+
+    key_length = 0
+
+    maxx = 0
+    maxy = 0
+    maxz = 0
+
+    curr_x = 0
+    curr_y = 0
+    curr_z = 0
+    grid = dict()
+
+    it = iter(map_raw_text)
+
+    # map block
+    for char in it:
+        if char == "\n":
+            in_comment_line = False
+            comment_trigger = False
+            continue
+        elif in_comment_line:
+            continue
+        elif char == "\t":
+            continue
+
+        if char == "/" and not in_quote_block:
+            if comment_trigger:
+                in_comment_line = True
+                continue
+            else:
+                comment_trigger = True
+        else:
+            comment_trigger = False
+
+        if in_data_block:
+
+            if in_varedit_block:
+
+                if in_quote_block:
+                    if char == "\\":
+                        curr_datum = curr_datum + char
+                        escaping = True
+
+                    elif escaping:
+                        curr_datum = curr_datum + char
+                        escaping = False
+
+                    elif char == "\"":
+                        curr_datum = curr_datum + char
+                        in_quote_block = False
+
+                    else:
+                        curr_datum = curr_datum + char
+
+                else:
+                    if skip_whitespace and char == " ":
+                        skip_whitespace = False
+                        continue
+                    skip_whitespace = False
+
+                    if char == "\"":
+                        curr_datum = curr_datum + char
+                        in_quote_block = True
+
+                    elif char == ";":
+                        skip_whitespace = True
+                        curr_datum = curr_datum + char
+
+                    elif char == "}":
+                        curr_datum = curr_datum + char
+                        in_varedit_block = False
+
+                    else:
+                        curr_datum = curr_datum + char
+
+            elif char == "{":
+                curr_datum = curr_datum + char
+                in_varedit_block = True
+
+            elif char == ",":
+                curr_data.append(curr_datum)
+                curr_datum = ""
+
+            elif char == ")":
+                curr_data.append(curr_datum)
+                curr_data = tuple(curr_data)
+                try:
+                    dictionary[curr_key] = curr_data
+                except bidict.ValueDuplicationError:
+                    # if the map has duplicate values, eliminate them now
+                    duplicate_keys[curr_key] = dictionary.inv[curr_data]
+                curr_data = list()
+                curr_datum = ""
+                curr_key = 0
+                curr_key_len = 0
+                in_data_block = False
+                after_data_block = True
+
+            else:
+                curr_datum = curr_datum + char
+
+        elif in_key_block:
+            if char == "\"":
+                in_key_block = False
+                if key_length == 0:
+                    key_length = curr_key_len
+                else:
+                    assert key_length == curr_key_len
+            else:
+                curr_key = BASE * curr_key + base52_r[char]
+                curr_key_len += 1
+
+        # else we're looking for a key block, a data block or the map block
+        elif char == "\"":
+            in_key_block = True
+            after_data_block = False
+
+        elif char == "(":
+            if after_data_block:
+                in_coord_block = True
+                after_data_block = False
+                curr_key = 0
+                curr_key_len = 0
+                break
+            else:
+                in_data_block = True
+                after_data_block = False
+
+    # grid block
+    for char in it:
+        if in_coord_block:
+            if char == ",":
+                if reading_coord == "x":
+                    curr_x = int(curr_num)
+                    if curr_x > maxx:
+                        maxx = curr_x
+                    iter_x = 0
+                    curr_num = ""
+                    reading_coord = "y"
+                elif reading_coord == "y":
+                    curr_y = int(curr_num)
+                    if curr_y > maxy:
+                        maxy = curr_y
+                    curr_num = ""
+                    reading_coord = "z"
+                else:
+                    raise ValueError("too many dimensions")
+
+            elif char == ")":
+                curr_z = int(curr_num)
+                if curr_z > maxz:
+                    maxz = curr_z
+                in_coord_block = False
+                reading_coord = "x"
+                curr_num = ""
+
+            else:
+                curr_num = curr_num + char
+
+        elif in_map_string:
+            if char == "\"":
+                in_map_string = False
+                adjust_y = True
+                curr_y -= 1
+
+            elif char == "\n":
+                if adjust_y:
+                    adjust_y = False
+                else:
+                    curr_y += 1
+                if curr_x > maxx:
+                    maxx = curr_x
+                if iter_x > 1:
+                    curr_x = 1
+                iter_x = 0
+
+            else:
+                curr_key = BASE * curr_key + base52_r[char]
+                curr_key_len += 1
+                if curr_key_len == key_length:
+                    iter_x += 1
+                    if iter_x > 1:
+                        curr_x += 1
+
+                    grid[curr_x, curr_y, curr_z] = duplicate_keys.get(curr_key, curr_key)
+                    curr_key = 0
+                    curr_key_len = 0
+
+        # else look for coordinate block or a map string
+        elif char == "(":
+            in_coord_block = True
+        elif char == "\"":
+            in_map_string = True
+
+    if curr_y > maxy:
+        maxy = curr_y
+
+    data = DMM(key_length, Coordinate(maxx, maxy, maxz))
+    data.dictionary = dictionary
+    data.grid = grid
+    return data
diff --git a/tools/mapmerge2/dmm2tgm.bat b/tools/mapmerge2/dmm2tgm.bat
new file mode 100644
index 0000000000..bcf6150c2e
--- /dev/null
+++ b/tools/mapmerge2/dmm2tgm.bat
@@ -0,0 +1,5 @@
+@echo off
+set MAPROOT=../../_maps/
+set TGM=1
+python convert.py
+pause
diff --git a/tools/mapmerge2/frontend.py b/tools/mapmerge2/frontend.py
new file mode 100644
index 0000000000..4d44eab951
--- /dev/null
+++ b/tools/mapmerge2/frontend.py
@@ -0,0 +1,127 @@
+# Common code for the frontend interface of map tools
+import sys
+import os
+import pathlib
+import shutil
+from collections import namedtuple
+
+Settings = namedtuple('Settings', ['map_folder', 'tgm'])
+MapsToRun = namedtuple('MapsToRun', ['files', 'indices'])
+
+def string_to_num(s):
+    try:
+        return int(s)
+    except ValueError:
+        return -1
+
+def read_settings():
+    # discover map folder if needed
+    try:
+        map_folder = os.environ['MAPROOT']
+    except KeyError:
+        map_folder = '_maps/'
+        for _ in range(8):
+            if os.path.exists(map_folder):
+                break
+            map_folder = os.path.join('..', map_folder)
+        else:
+            map_folder = None
+
+    # assume TGM is True by default
+    tgm = os.environ.get('TGM', "1") == "1"
+
+    return Settings(map_folder, tgm)
+
+def pretty_path(settings, path_str):
+    if settings.map_folder:
+        return path_str[len(os.path.commonpath([settings.map_folder, path_str]))+1:]
+    else:
+        return path_str
+
+def prompt_maps(settings, verb):
+    if not settings.map_folder:
+        print("Could not autodetect the _maps folder, set MAPROOT")
+        exit(1)
+
+    list_of_files = list()
+    for root, directories, filenames in os.walk(settings.map_folder):
+        for filename in [f for f in filenames if f.endswith(".dmm")]:
+            list_of_files.append(pathlib.Path(root, filename))
+
+    last_dir = ""
+    for i, this_file in enumerate(list_of_files):
+        this_dir = this_file.parent
+        if last_dir != this_dir:
+            print("--------------------------------")
+            last_dir = this_dir
+        print("[{}]: {}".format(i, pretty_path(settings, str(this_file))))
+
+    print("--------------------------------")
+    in_list = input("List the maps you want to " + verb + " (example: 1,3-5,12):\n")
+    in_list = in_list.replace(" ", "")
+    in_list = in_list.split(",")
+
+    valid_indices = list()
+    for m in in_list:
+        index_range = m.split("-")
+        if len(index_range) == 1:
+            index = string_to_num(index_range[0])
+            if index >= 0 and index < len(list_of_files):
+                valid_indices.append(index)
+        elif len(index_range) == 2:
+            index0 = string_to_num(index_range[0])
+            index1 = string_to_num(index_range[1])
+            if index0 >= 0 and index0 <= index1 and index1 < len(list_of_files):
+                valid_indices.extend(range(index0, index1 + 1))
+
+    return MapsToRun(list_of_files, valid_indices)
+
+def process(settings, verb, *, modify=True, backup=None):
+    if backup is None:
+        backup = modify  # by default, backup when we modify
+    assert modify or not backup  # doesn't make sense to backup when not modifying
+
+    if len(sys.argv) > 1:
+        maps = sys.argv[1:]
+    else:
+        maps = prompt_maps(settings, verb)
+        maps = [str(maps.files[i]) for i in maps.indices]
+        print()
+
+    if not maps:
+        print("No maps selected.")
+        return
+
+    if modify:
+        print(f"Maps WILL{'' if settings.tgm else ' NOT'} be converted to tgm.")
+        if backup:
+            print("Backups will be created with a \".before\" extension.")
+        else:
+            print("Warning: backups are NOT being taken.")
+
+    print(f"\nWill {verb} these maps:")
+    for path_str in maps:
+        print(pretty_path(settings, path_str))
+
+    try:
+        confirm = input(f"\nPress Enter to {verb}...\n")
+    except KeyboardInterrupt:
+        confirm = "^C"
+    if confirm != "":
+        print(f"\nAborted.")
+        return
+
+    for path_str in maps:
+        print(f' - {pretty_path(settings, path_str)}')
+
+        if backup:
+            shutil.copyfile(path_str, path_str + ".before")
+
+        try:
+            yield path_str
+        except Exception as e:
+            print(f"Error: {e}")
+        else:
+            print("Succeeded.")
+
+    print("\nFinished.")
diff --git a/tools/mapmerge2/mapmerge.bat b/tools/mapmerge2/mapmerge.bat
new file mode 100644
index 0000000000..5a066226b3
--- /dev/null
+++ b/tools/mapmerge2/mapmerge.bat
@@ -0,0 +1,5 @@
+@echo off
+set MAPROOT=../../_maps/
+set TGM=1
+python mapmerge.py
+pause
diff --git a/tools/mapmerge2/mapmerge.py b/tools/mapmerge2/mapmerge.py
new file mode 100644
index 0000000000..ccfbfec784
--- /dev/null
+++ b/tools/mapmerge2/mapmerge.py
@@ -0,0 +1,93 @@
+#!/usr/bin/env python3
+import frontend
+import shutil
+from dmm import *
+from collections import defaultdict
+
+def merge_map(new_map, old_map, delete_unused=False):
+    if new_map.key_length != old_map.key_length:
+        print("Warning: Key lengths differ, taking new map")
+        print(f"  Old: {old_map.key_length}")
+        print(f"  New: {new_map.key_length}")
+        return new_map
+
+    if new_map.size != old_map.size:
+        print("Warning: Map dimensions differ, taking new map")
+        print(f"  Old: {old_map.size}")
+        print(f"  New: {new_map.size}")
+        return new_map
+
+    key_length, size = old_map.key_length, old_map.size
+    merged = DMM(key_length, size)
+    merged.dictionary = old_map.dictionary.copy()
+
+    known_keys = dict()  # mapping fron 'new' key to 'merged' key
+    unused_keys = set(old_map.dictionary.keys())  # keys going unused
+
+    # step one: parse the new version, compare it to the old version, merge both
+    for z, y, x in new_map.coords_zyx:
+        new_key = new_map.grid[x, y, z]
+        # if this key has been processed before, it can immediately be merged
+        try:
+            merged.grid[x, y, z] = known_keys[new_key]
+            continue
+        except KeyError:
+            pass
+
+        def select_key(assigned):
+            merged.grid[x, y, z] = known_keys[new_key] = assigned
+
+        old_key = old_map.grid[x, y, z]
+        old_tile = old_map.dictionary[old_key]
+        new_tile = new_map.dictionary[new_key]
+
+        # this tile is the exact same as before, so the old key is used
+        if new_tile == old_tile:
+            select_key(old_key)
+            unused_keys.remove(old_key)
+
+        # the tile is different here, but if it exists in the merged dictionary, that key can be used
+        elif new_tile in merged.dictionary.inv:
+            newold_key = merged.dictionary.inv[new_tile]
+            select_key(newold_key)
+            unused_keys.remove(newold_key)
+
+        # the tile is brand new and it needs a new key, but if the old key isn't being used any longer it can be used instead
+        elif old_tile not in new_map.dictionary.inv and old_key in unused_keys:
+            merged.dictionary[old_key] = new_tile
+            select_key(old_key)
+            unused_keys.remove(old_key)
+
+        # all other options ruled out, a brand new key is generated for the brand new tile
+        else:
+            fresh_key = merged.generate_new_key()
+            merged.dictionary[fresh_key] = new_tile
+            select_key(fresh_key)
+
+    # step two: delete unused keys
+    if unused_keys:
+        print(f"Notice: Trimming {len(unused_keys)} unused dictionary keys.")
+        for key in unused_keys:
+            del merged.dictionary[key]
+
+    # sanity check: that the merged map equals the new map
+    for z, y, x in new_map.coords_zyx:
+        new_tile = new_map.dictionary[new_map.grid[x, y, z]]
+        merged_tile = merged.dictionary[merged.grid[x, y, z]]
+        if new_tile != merged_tile:
+            print(f"Error: the map has been mangled! This is a mapmerge bug!")
+            print(f"At {x},{y},{z}.")
+            print(f"Should be {new_tile}")
+            print(f"Instead is {merged_tile}")
+            raise RuntimeError()
+
+    return merged
+
+def main(settings):
+    for fname in frontend.process(settings, "merge", backup=True):
+        old_map = DMM.from_file(fname + ".backup")
+        new_map = DMM.from_file(fname)
+        merge_map(old_map, new_map).to_file(fname, settings.tgm)
+
+if __name__ == '__main__':
+    main(frontend.read_settings())
diff --git a/tools/mapmerge2/precommit.py b/tools/mapmerge2/precommit.py
new file mode 100644
index 0000000000..381f1ea8a3
--- /dev/null
+++ b/tools/mapmerge2/precommit.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+import os
+import pygit2
+import dmm
+from mapmerge import merge_map
+
+def main(repo):
+    if repo.index.conflicts:
+        print("You need to resolve merge conflicts first.")
+        return 1
+
+    changed = 0
+    for path, status in repo.status().items():
+        if path.endswith(".dmm") and (status & (pygit2.GIT_STATUS_INDEX_MODIFIED | pygit2.GIT_STATUS_INDEX_NEW)):
+            # read the index
+            index_entry = repo.index[path]
+            index_map = dmm.DMM.from_bytes(repo[index_entry.id].read_raw())
+
+            try:
+                head_blob = repo[repo[repo.head.target].tree[path].id]
+            except KeyError:
+                # New map, no entry in HEAD
+                print(f"Converting new map: {path}")
+                assert (status & pygit2.GIT_STATUS_INDEX_NEW)
+                merged_map = index_map
+            else:
+                # Entry in HEAD, merge the index over it
+                print(f"Merging map: {path}")
+                assert not (status & pygit2.GIT_STATUS_INDEX_NEW)
+                head_map = dmm.DMM.from_bytes(head_blob.read_raw())
+                merged_map = merge_map(index_map, head_map)
+
+            # write to the index
+            blob_id = repo.create_blob(merged_map.to_bytes())
+            repo.index.add(pygit2.IndexEntry(path, blob_id, index_entry.mode))
+            changed += 1
+
+            # write to the working directory if that's clean
+            if status & (pygit2.GIT_STATUS_WT_DELETED | pygit2.GIT_STATUS_WT_MODIFIED):
+                print(f"Warning: {path} has unindexed changes, not overwriting them")
+            else:
+                merged_map.to_file(os.path.join(repo.workdir, path))
+
+    if changed:
+        repo.index.write()
+        print(f"Merged {changed} maps.")
+    return 0
+
+if __name__ == '__main__':
+    exit(main(pygit2.Repository(pygit2.discover_repository(os.getcwd()))))
diff --git a/tools/mapmerge2/requirements-install.bat b/tools/mapmerge2/requirements-install.bat
new file mode 100644
index 0000000000..71341af879
--- /dev/null
+++ b/tools/mapmerge2/requirements-install.bat
@@ -0,0 +1,3 @@
+@echo off
+python -m pip install -r requirements.txt
+pause
diff --git a/tools/mapmerge2/requirements.txt b/tools/mapmerge2/requirements.txt
new file mode 100644
index 0000000000..d01a2c6ccf
--- /dev/null
+++ b/tools/mapmerge2/requirements.txt
@@ -0,0 +1,2 @@
+pygit2==0.26.0
+bidict==0.13.1
diff --git a/tools/mapmerge2/tgm2dmm.bat b/tools/mapmerge2/tgm2dmm.bat
new file mode 100644
index 0000000000..2748533feb
--- /dev/null
+++ b/tools/mapmerge2/tgm2dmm.bat
@@ -0,0 +1,5 @@
+@echo off
+set MAPROOT=../../_maps/
+set TGM=0
+python convert.py
+pause