fix: detect prereleases on GitHub so we can ignore them

This is simple enough: we just use the GitHub releases API that does
actually have the info in it.

I have complained about the feed not having the info here:
https://github.com/orgs/community/discussions/88765

nix_update/version/github.py

@@ -1,23 +1,20 @@
+import json
 import re
 import urllib.request
 import xml.etree.ElementTree as ET
-from urllib.parse import ParseResult, unquote, urlparse
-from xml.etree.ElementTree import Element
+from urllib.parse import ParseResult, urlparse
 
-from ..errors import VersionError
 from ..utils import info
 from .version import Version
 
 
-def version_from_entry(entry: Element) -> Version:
-    if entry is None:
-        raise VersionError("No release found")
-    link = entry.find("{http://www.w3.org/2005/Atom}link")
-    assert link is not None
-    href = link.attrib["href"]
-    url = urlparse(href)
-    # TODO: set pre-release flag
-    return Version(unquote(url.path.split("/")[-1]))
+def version_from_entry(entry: dict) -> Version:
+    href = entry["html_url"]
+    assert href is not None
+    prerelease = entry["prerelease"]
+    draft = entry["draft"]
+    version = entry["tag_name"]
+    return Version(version, prerelease=prerelease or draft)
 
 
 def fetch_github_versions(url: ParseResult) -> list[Version]:
@@ -27,11 +24,19 @@ def fetch_github_versions(url: ParseResult) -> list[Version]:
     owner, repo = parts[1], parts[2]
     repo = re.sub(r"\.git$", "", repo)
     # TODO fallback to tags?
-    feed_url = f"https://github.com/{owner}/{repo}/releases.atom"
-    info(f"fetch {feed_url}")
-    resp = urllib.request.urlopen(feed_url)
-    tree = ET.fromstring(resp.read())
-    releases = tree.findall(".//{http://www.w3.org/2005/Atom}entry")
+    # https://docs.github.com/en/rest/releases/releases?apiVersion=2022-11-28#list-releases
+    releases_url = f"https://api.github.com/repos/{owner}/{repo}/releases?per_page=100"
+    info(f"fetch {releases_url}")
+    req = urllib.request.Request(
+        releases_url,
+        headers={
+            "Accept": "application/vnd.github+json",
+            "X-GitHub-Api-Version": "2022-11-28",
+        },
+    )
+    resp = urllib.request.urlopen(req)
+    releases = json.loads(resp.read())
+
     return [version_from_entry(x) for x in releases]