[llvm] workflows: Add a simple pull request subscription workflow (PR #64913)

[Fangrui Song via llvm-commits]

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@@ -65,6 +66,30 @@ def run(self) -> bool:
         return False
 
 
+class PRSubscriber:
+    @property
+    def team_name(self) -> str:
+        return self._team_name
+
+    def __init__(self, token: str, repo: str, pr_number: int, label_name : str):
+        self.repo = github.Github(token).get_repo(repo)
+        self.org = github.Github(token).get_organization(self.repo.organization.login)
+        self.pr = self.repo.get_issue(pr_number).as_pull_request()
+        self._team_name = "pr-subscribers-{}".format(label_name).lower()
+
+    def run(self) -> bool:
+        for team in self.org.get_teams():
+            if self.team_name != team.name.lower():
+                continue
+            try:
+                patch = requests.get(self.pr.diff_url).text
+            except:
+                patch = ""
+            comment = "@llvm/{}".format(team.slug) + "\n\n<details><summary>Changes</summary><pre>\n" + patch + "\n</pre></details>"
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MaskRay wrote:

Does the `diff` variable contain `` ``` ``? If not, maybe add `` ```diff `` and `` ``` ``

https://github.com/llvm/llvm-project/pull/64913