[lua] Automate release and version retrieval (#372)

Using https://www.lua.org/versions.html.

src/lua.py

@@ -0,0 +1,24 @@
+import re
+
+from bs4 import BeautifulSoup
+from common import dates, http, releasedata
+
+"""Fetches Lua releases from lua.org."""
+
+RELEASED_AT_PATTERN = re.compile(r"Lua\s*(?P<release>\d+\.\d+)\s*was\s*released\s*on\s*(?P<release_date>\d+\s*\w+\s*\d{4})")
+VERSION_PATTERN = re.compile(r"(?P<version>\d+\.\d+\.\d+),\s*released\s*on\s*(?P<version_date>\d+\s*\w+\s*\d{4})")
+
+with releasedata.ProductData("lua") as product_data:
+    page = http.fetch_url("https://www.lua.org/versions.html")
+    soup = BeautifulSoup(page.text, 'html.parser')
+    page_text = soup.text # HTML is broken, no way to parse it with beautifulsoup
+
+    for release_match in RELEASED_AT_PATTERN.finditer(page_text):
+        release = release_match.group('release')
+        release_date = dates.parse_date(release_match.group('release_date'))
+        product_data.get_release(release).set_release_date(release_date)
+
+    for version_match in VERSION_PATTERN.finditer(page_text):
+        version = version_match.group('version')
+        version_date = dates.parse_date(version_match.group('version_date'))
+        product_data.declare_version(version, version_date)