Use svn to collects tags in GitHubTagsAPI

Surprisingly, GitHub allows svn requests to repositories. Now we can
have all the tags with a single request. This is much more efficient and
gentle to the APIs.

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

Author: Hritik14

requirements.txt

@@ -17,3 +17,4 @@ toml>=0.10.2
 lxml>=4.6.3
 gunicorn>=20.1.0
 django-environ==0.4.5
+defusedxml==0.7.1

vulnerabilities/package_managers.py

@@ -24,6 +24,7 @@
 import xml.etree.ElementTree as ET
 from datetime import datetime
 from json import JSONDecodeError
+from subprocess import check_output
 from typing import List
 from typing import Mapping
 from typing import Set
@@ -377,42 +378,20 @@ class GitHubTagsAPI(VersionAPI):
 
     package_type = "github"
 
-    async def fetch(self, owner_repo: str, session, endpoint=None) -> None:
+    async def fetch(self, owner_repo: str, session) -> None:
         """
         owner_repo is a string of format "{repo_owner}/{repo_name}"
         Example value of owner_repo = "nexB/scancode-toolkit"
         """
         self.cache[owner_repo] = set()
-        if not endpoint:
-            endpoint = f"https://github.com/{owner_repo}/tags"
-        resp = await session.get(endpoint)
-        resp = await resp.read()
-
-        soup = BeautifulSoup(resp, features="lxml")
-        for release_entry in soup.find_all("div", {"class": "commit"}):
-            version = None
-            for links in release_entry.find_all("a"):
-                if f"/{owner_repo}/releases/tag/" in links["href"].lower():
-                    prefix, _slash, version = links["href"].rpartition("/")
-                    version = version.lstrip("v")
-                    break
-
-            release_date = release_entry.find("relative-time")["datetime"]
-            self.cache[owner_repo].add(
-                Version(value=version, release_date=dateparser.parse(release_date))
-            )
-
-        url = None
-        pagination_links = soup.find("div", {"class": "paginate-container"}).find_all("a")
-        for link in pagination_links:
-            if link.text == "Next":
-                url = link["href"]
-                break
-
-        if url:
-            # FIXME: this could be asynced to improve performance
-            await self.fetch(owner_repo, session, url)
-
+        endpoint = f"https://github.com/{owner_repo}"
+
+        tags_xml = check_output(['svn', 'ls', '--xml', f"{endpoint}/tags"], text=True)
+        elements = ET.fromstring(tags_xml)
+        for entry in elements.iter("entry"):
+            name = entry.find("name").text
+            release_date = dateparser.parse(entry.find("commit/date").text)
+            self.cache[owner_repo].add(Version(value=name, release_date=release_date))
 
 class HexVersionAPI(VersionAPI):
     async def fetch(self, pkg, session):