Add script to generate files in translations folder

Unfortunately anchors are discarded while parsing YAML, so regex is used to pick out the relevant lines.

.gitignore

@@ -213,3 +213,5 @@ pip-log.txt
 
 #Mr Developer
 .mr.developer.cfg
+
+.venv

README.md

@@ -2,4 +2,24 @@
 
 This repository holds the masterlist prelude, a metadata file that is used to supply common metadata to all masterlists.
 
-See [CONTRIBUTING.md](CONTRIBUTING.md) for information on how to contribute to the prelude.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for information on how to contribute to the prelude.
+
+### Synchronising Weblate translations
+
+The `translations` directory holds files that are read and written by [Weblate](https://hosted.weblate.org/projects/loot/prelude/). There's a script that can be used to regenerate their content from `prelude.yaml`.
+
+To use the scripts, first install their dependencies in a virtual environment. On Windows, make sure Python 3 is installed, then run:
+
+```
+py -m venv .venv
+.\.venv\Scripts\activate
+pip install -r requirements.txt
+```
+
+To regenerate the files in the `translations` directory from `prelude.yaml`, run:
+
+```
+py scripts/export-translations.py
+```
+
+The script makes assumptions about the formatting and layout of entries in `prelude.yaml`, so it's worth double-checking its changes.

requirements.txt

@@ -0,0 +1 @@
+pyyaml==6.0.1

scripts/export-translations.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Read localised message content strings from prelude.yaml and generate
+# translations/messages.<lang>.yaml files from them.
+import math
+import re
+
+from yaml import dump
+
+# This makes some assumptions about the prelude.yaml:
+# - anchors are always separated from anything before them by at least one space
+# - message content objects are listed with the lang as the first key, followed
+#   by the text
+# - message content text is enclosed in single quotes
+
+messages = {}
+with open('prelude.yaml', encoding='utf8') as input:
+    lines = input.readlines()
+
+    anchor = None
+    lang = None
+    for line in lines:
+        match = re.search(r' &([^\s]+)$', line)
+        if match != None:
+            anchor = match.group(1)
+            lang = None
+            text = None
+            continue
+
+        match = re.search(r'- lang: ([a-zA-Z_]+)', line)
+        if match != None:
+            lang = match.group(1)
+            text = None
+            continue
+
+        match = re.search(r' text: \'(.+)\'', line)
+        if match != None:
+            text = match.group(1).replace("''", "'")
+
+        if anchor and lang and text:
+            if lang in messages:
+                messages[lang][anchor] = text
+            else:
+                messages[lang] = { anchor: text }
+
+for lang in messages:
+    with open(f'translations/messages.{lang}.yaml', mode='w', encoding='utf8') as output:
+        dump(messages[lang], output, allow_unicode=True, width=math.inf)